[LARGE!] symbolic magic

Message-Id: <200105191912.UAA23925@gizmo.fdgroup.co.uk>

p4raw-id: //depot/perl@10168

23 files changed, 427 insertions, 271 deletions

diff --git a/av.c b/av.c
index 273fed94eb..086c75e56f 100644
--- a/av.c
+++ b/av.c
@@ -25,7 +25,7 @@ Perl_av_reify(pTHX_ AV *av)
     if (AvREAL(av))
 	return;
 #ifdef DEBUGGING
-    if (SvTIED_mg((SV*)av, 'P') && ckWARN_d(WARN_DEBUGGING))
+    if (SvTIED_mg((SV*)av, PERL_MAGIC_tied) && ckWARN_d(WARN_DEBUGGING))
 	Perl_warner(aTHX_ WARN_DEBUGGING, "av_reify called on tied array");
 #endif
     key = AvMAX(av) + 1;
@@ -57,7 +57,7 @@ void
 Perl_av_extend(pTHX_ AV *av, I32 key)
 {
     MAGIC *mg;
-    if ((mg = SvTIED_mg((SV*)av, 'P'))) {
+    if ((mg = SvTIED_mg((SV*)av, PERL_MAGIC_tied))) {
 	dSP;
 	ENTER;
 	SAVETMPS;
@@ -185,7 +185,9 @@ Perl_av_fetch(pTHX_ register AV *av, I32 key, I32 lval)
     }
 
     if (SvRMAGICAL(av)) {
-	if (mg_find((SV*)av,'P') || mg_find((SV*)av,'D')) {
+	if (mg_find((SV*)av, PERL_MAGIC_tied) ||
+		mg_find((SV*)av, PERL_MAGIC_regdata))
+	{
 	    sv = sv_newmortal();
 	    mg_copy((SV*)av, sv, 0, key);
 	    PL_av_fetch_sv = sv;
@@ -253,7 +255,7 @@ Perl_av_store(pTHX_ register AV *av, I32 key, SV *val)
 	Perl_croak(aTHX_ PL_no_modify);
 
     if (SvRMAGICAL(av)) {
-	if (mg_find((SV*)av,'P')) {
+	if (mg_find((SV*)av, PERL_MAGIC_tied)) {
 	    if (val != &PL_sv_undef) {
 		mg_copy((SV*)av, val, 0, key);
 	    }
@@ -438,7 +440,7 @@ Perl_av_undef(pTHX_ register AV *av)
     /*SUPPRESS 560*/
 
     /* Give any tie a chance to cleanup first */
-    if (SvTIED_mg((SV*)av, 'P')) 
+    if (SvTIED_mg((SV*)av, PERL_MAGIC_tied)) 
 	av_fill(av, -1);   /* mg_clear() ? */
 
     if (AvREAL(av)) {
@@ -474,7 +476,7 @@ Perl_av_push(pTHX_ register AV *av, SV *val)
     if (SvREADONLY(av))
 	Perl_croak(aTHX_ PL_no_modify);
 
-    if ((mg = SvTIED_mg((SV*)av, 'P'))) {
+    if ((mg = SvTIED_mg((SV*)av, PERL_MAGIC_tied))) {
 	dSP;
 	PUSHSTACKi(PERLSI_MAGIC);
 	PUSHMARK(SP);
@@ -510,7 +512,7 @@ Perl_av_pop(pTHX_ register AV *av)
 	return &PL_sv_undef;
     if (SvREADONLY(av))
 	Perl_croak(aTHX_ PL_no_modify);
-    if ((mg = SvTIED_mg((SV*)av, 'P'))) {
+    if ((mg = SvTIED_mg((SV*)av, PERL_MAGIC_tied))) {
 	dSP;    
 	PUSHSTACKi(PERLSI_MAGIC);
 	PUSHMARK(SP);
@@ -556,7 +558,7 @@ Perl_av_unshift(pTHX_ register AV *av, register I32 num)
     if (SvREADONLY(av))
 	Perl_croak(aTHX_ PL_no_modify);
 
-    if ((mg = SvTIED_mg((SV*)av, 'P'))) {
+    if ((mg = SvTIED_mg((SV*)av, PERL_MAGIC_tied))) {
 	dSP;
 	PUSHSTACKi(PERLSI_MAGIC);
 	PUSHMARK(SP);
@@ -622,7 +624,7 @@ Perl_av_shift(pTHX_ register AV *av)
 	return &PL_sv_undef;
     if (SvREADONLY(av))
 	Perl_croak(aTHX_ PL_no_modify);
-    if ((mg = SvTIED_mg((SV*)av, 'P'))) {
+    if ((mg = SvTIED_mg((SV*)av, PERL_MAGIC_tied))) {
 	dSP;
 	PUSHSTACKi(PERLSI_MAGIC);
 	PUSHMARK(SP);
@@ -680,7 +682,7 @@ Perl_av_fill(pTHX_ register AV *av, I32 fill)
 	Perl_croak(aTHX_ "panic: null array");
     if (fill < 0)
 	fill = -1;
-    if ((mg = SvTIED_mg((SV*)av, 'P'))) {
+    if ((mg = SvTIED_mg((SV*)av, PERL_MAGIC_tied))) {
 	dSP;            
 	ENTER;
 	SAVETMPS;
@@ -743,13 +745,14 @@ Perl_av_delete(pTHX_ AV *av, I32 key, I32 flags)
     }
     if (SvRMAGICAL(av)) {
 	SV **svp;
-	if ((mg_find((SV*)av,'P') || mg_find((SV*)av,'D'))
+	if ((mg_find((SV*)av, PERL_MAGIC_tied) ||
+		mg_find((SV*)av, PERL_MAGIC_regdata))
 	    && (svp = av_fetch(av, key, TRUE)))
 	{
 	    sv = *svp;
 	    mg_clear(sv);
-	    if (mg_find(sv, 'p')) {
-		sv_unmagic(sv, 'p');		/* No longer an element */
+	    if (mg_find(sv, PERL_MAGIC_tiedelem)) {
+		sv_unmagic(sv, PERL_MAGIC_tiedelem);	/* No longer an element */
 		return sv;
 	    }
 	    return Nullsv;			/* element cannot be deleted */
@@ -797,12 +800,14 @@ Perl_av_exists(pTHX_ AV *av, I32 key)
 	    return FALSE;
     }
     if (SvRMAGICAL(av)) {
-	if (mg_find((SV*)av,'P') || mg_find((SV*)av,'D')) {
+	if (mg_find((SV*)av, PERL_MAGIC_tied) ||
+		mg_find((SV*)av, PERL_MAGIC_regdata))
+	{
 	    SV *sv = sv_newmortal();
 	    MAGIC *mg;
 
 	    mg_copy((SV*)av, sv, 0, key);
-	    mg = mg_find(sv, 'p');
+	    mg = mg_find(sv, PERL_MAGIC_tiedelem);
 	    if (mg) {
 		magic_existspack(sv, mg);
 		return SvTRUE(sv);
diff --git a/cc_runtime.h b/cc_runtime.h
index dbc7475774..799bf463d8 100644
--- a/cc_runtime.h
+++ b/cc_runtime.h
@@ -14,7 +14,7 @@
 
 #define MAYBE_TAINT_SASSIGN_SRC(sv) \
     if (PL_tainting && PL_tainted && (!SvGMAGICAL(left) || !SvSMAGICAL(left) || \
-                                !((mg=mg_find(left, 't')) && mg->mg_len & 1)))\
+        !((mg=mg_find(left, PERL_MAGIC_taint)) && mg->mg_len & 1)))\
         TAINT_NOT
 
 #define PP_PREINC(sv) do {	\
diff --git a/doop.c b/doop.c
index 9550b3e390..2b504a1b69 100644
--- a/doop.c
+++ b/doop.c
@@ -1291,7 +1291,7 @@ Perl_do_kv(pTHX)
 	if (PL_op->op_flags & OPf_MOD || LVRET) {	/* lvalue */
 	    if (SvTYPE(TARG) < SVt_PVLV) {
 		sv_upgrade(TARG, SVt_PVLV);
-		sv_magic(TARG, Nullsv, 'k', Nullch, 0);
+		sv_magic(TARG, Nullsv, PERL_MAGIC_nkeys, Nullch, 0);
 	    }
 	    LvTYPE(TARG) = 'k';
 	    if (LvTARG(TARG) != (SV*)keys) {
@@ -1303,7 +1303,7 @@ Perl_do_kv(pTHX)
 	    RETURN;
 	}
 
-	if (! SvTIED_mg((SV*)keys, 'P'))
+	if (! SvTIED_mg((SV*)keys, PERL_MAGIC_tied))
 	    i = HvKEYS(keys);
 	else {
 	    i = 0;
diff --git a/dump.c b/dump.c
index 1b51b49cce..0e11589cca 100644
--- a/dump.c
+++ b/dump.c
@@ -706,6 +706,49 @@ Perl_gv_dump(pTHX_ GV *gv)
     Perl_dump_indent(aTHX_ 0, Perl_debug_log, "}\n");
 }
 
+
+/* map magic types to the symbolic name
+ * (with the PERL_MAGIC_ prefixed stripped)
+ */
+
+static struct { char type; char *name; } magic_names[] = {
+	PERL_MAGIC_sv,             "sv(\\0)",
+	PERL_MAGIC_arylen,         "arylen(#)",
+	PERL_MAGIC_glob,           "glob(*)",
+	PERL_MAGIC_pos,            "pos(.)",
+	PERL_MAGIC_backref,        "backref(<)",
+	PERL_MAGIC_overload,       "overload(A)",
+	PERL_MAGIC_bm,             "bm(B)",
+	PERL_MAGIC_regdata,        "regdata(D)",
+	PERL_MAGIC_env,            "env(E)",
+	PERL_MAGIC_isa,            "isa(I)",
+	PERL_MAGIC_dbfile,         "dbfile(L)",
+	PERL_MAGIC_tied,           "tied(P)",
+	PERL_MAGIC_sig,            "sig(S)",
+	PERL_MAGIC_uvar,           "uvar(U)",
+	PERL_MAGIC_overload_elem,  "overload_elem(a)",
+	PERL_MAGIC_overload_table, "overload_table(c)",
+	PERL_MAGIC_regdatum,       "regdatum(d)",
+	PERL_MAGIC_envelem,        "envelem(e)",
+	PERL_MAGIC_fm,             "fm(f)",
+	PERL_MAGIC_regex_global,   "regex_global(g)",
+	PERL_MAGIC_isaelem,        "isaelem(i)",
+	PERL_MAGIC_nkeys,          "nkeys(k)",
+	PERL_MAGIC_dbline,         "dbline(l)",
+	PERL_MAGIC_mutex,          "mutex(m)",
+	PERL_MAGIC_collxfrm,       "collxfrm(o)",
+	PERL_MAGIC_tiedelem,       "tiedelem(p)",
+	PERL_MAGIC_tiedscalar,     "tiedscalar(q)",
+	PERL_MAGIC_qr,             "qr(r)",
+	PERL_MAGIC_sigelem,        "sigelem(s)",
+	PERL_MAGIC_taint,          "taint(t)",
+	PERL_MAGIC_vec,            "vec(v)",
+	PERL_MAGIC_substr,         "substr(x)",
+	PERL_MAGIC_defelem,        "defelem(y)",
+	PERL_MAGIC_ext,            "ext(~)",
+	0,			   0 /* this null string terminates the list */
+};
+
 void
 Perl_do_magic_dump(pTHX_ I32 level, PerlIO *file, MAGIC *mg, I32 nest, I32 maxnest, bool dumpops, STRLEN pvlim)
 {
@@ -753,10 +796,22 @@ Perl_do_magic_dump(pTHX_ I32 level, PerlIO *file, MAGIC *mg, I32 nest, I32 maxne
 	if (mg->mg_private)
 	    Perl_dump_indent(aTHX_ level, file, "    MG_PRIVATE = %d\n", mg->mg_private);
 
-	if (isPRINT(mg->mg_type))
-	    Perl_dump_indent(aTHX_ level, file, "    MG_TYPE = '%c'\n", mg->mg_type);
-	else
-	    Perl_dump_indent(aTHX_ level, file, "    MG_TYPE = '\\%o'\n", mg->mg_type);
+	{
+	    int n;
+	    char *name = 0;
+	    for (n=0; magic_names[n].name; n++) {
+		if (mg->mg_type == magic_names[n].type) {
+		    name = magic_names[n].name;
+		    break;
+		}
+	    }
+	    if (name)
+		Perl_dump_indent(aTHX_ level, file,
+				"    MG_TYPE = PERL_MAGIC_%s\n", name);
+	    else
+		Perl_dump_indent(aTHX_ level, file,
+				"    MG_TYPE = UNKNOWN(\\%o)\n", mg->mg_type);
+	}
 
         if (mg->mg_flags) {
             Perl_dump_indent(aTHX_ level, file, "    MG_FLAGS = 0x%02X\n", mg->mg_flags);
diff --git a/gv.c b/gv.c
index 462002c5d5..2f31585c51 100644
--- a/gv.c
+++ b/gv.c
@@ -80,7 +80,7 @@ Perl_gv_fetchfile(pTHX_ const char *name)
 	gv_init(gv, PL_defstash, tmpbuf, tmplen, FALSE);
 	sv_setpv(GvSV(gv), name);
 	if (PERLDB_LINE)
-	    hv_magic(GvHVn(gv_AVadd(gv)), Nullgv, 'L');
+	    hv_magic(GvHVn(gv_AVadd(gv)), Nullgv, PERL_MAGIC_dbfile);
     }
     if (tmpbuf != smallbuf)
 	Safefree(tmpbuf);
@@ -110,7 +110,7 @@ Perl_gv_init(pTHX_ GV *gv, HV *stash, const char *name, STRLEN len, int multi)
     GvFILE(gv) = CopFILE(PL_curcop) ? CopFILE(PL_curcop) : "";
     GvCVGEN(gv) = 0;
     GvEGV(gv) = gv;
-    sv_magic((SV*)gv, (SV*)gv, '*', Nullch, 0);
+    sv_magic((SV*)gv, (SV*)gv, PERL_MAGIC_glob, Nullch, 0);
     GvSTASH(gv) = (HV*)SvREFCNT_inc(stash);
     GvNAME(gv) = savepvn(name, len);
     GvNAMELEN(gv) = len;
@@ -752,7 +752,7 @@ Perl_gv_fetchpv(pTHX_ const char *nambeg, I32 add, I32 sv_type)
 	if (strEQ(name, "ISA")) {
 	    AV* av = GvAVn(gv);
 	    GvMULTI_on(gv);
-	    sv_magic((SV*)av, (SV*)gv, 'I', Nullch, 0);
+	    sv_magic((SV*)av, (SV*)gv, PERL_MAGIC_isa, Nullch, 0);
 	    /* NOTE: No support for tied ISA */
 	    if ((add & GV_ADDMULTI) && strEQ(nambeg,"AnyDBM_File::ISA")
 		&& AvFILLp(av) == -1)
@@ -775,7 +775,7 @@ Perl_gv_fetchpv(pTHX_ const char *nambeg, I32 add, I32 sv_type)
         if (strEQ(name, "OVERLOAD")) {
             HV* hv = GvHVn(gv);
             GvMULTI_on(gv);
-            hv_magic(hv, Nullgv, 'A');
+            hv_magic(hv, Nullgv, PERL_MAGIC_overload);
         }
         break;
     case 'S':
@@ -789,7 +789,7 @@ Perl_gv_fetchpv(pTHX_ const char *nambeg, I32 add, I32 sv_type)
 	    }
 	    GvMULTI_on(gv);
 	    hv = GvHVn(gv);
-	    hv_magic(hv, Nullgv, 'S');
+	    hv_magic(hv, Nullgv, PERL_MAGIC_sig);
 	    for (i = 1; i < SIG_SIZE; i++) {
 	    	SV ** init;
 	    	init = hv_fetch(hv, PL_sig_name[i], strlen(PL_sig_name[i]), 1);
@@ -848,7 +848,7 @@ Perl_gv_fetchpv(pTHX_ const char *nambeg, I32 add, I32 sv_type)
 	   now (rather than going to magicalize)
 	*/
 
-	sv_magic(GvSV(gv), (SV*)gv, 0, name, len);
+	sv_magic(GvSV(gv), (SV*)gv, PERL_MAGIC_sv, name, len);
 
 	if (sv_type == SVt_PVHV)
 	    require_errno(gv);
@@ -859,7 +859,7 @@ Perl_gv_fetchpv(pTHX_ const char *nambeg, I32 add, I32 sv_type)
 	    break;
 	else {
             AV* av = GvAVn(gv);
-            sv_magic((SV*)av, Nullsv, 'D', Nullch, 0);
+            sv_magic((SV*)av, Nullsv, PERL_MAGIC_regdata, Nullch, 0);
 	    SvREADONLY_on(av);
         }
 	goto magicalize;
@@ -917,7 +917,7 @@ Perl_gv_fetchpv(pTHX_ const char *nambeg, I32 add, I32 sv_type)
 	    break;
 	else {
             AV* av = GvAVn(gv);
-            sv_magic((SV*)av, (SV*)av, 'D', Nullch, 0);
+            sv_magic((SV*)av, (SV*)av, PERL_MAGIC_regdata, Nullch, 0);
 	    SvREADONLY_on(av);
         }
 	/* FALL THROUGH */
@@ -933,7 +933,7 @@ Perl_gv_fetchpv(pTHX_ const char *nambeg, I32 add, I32 sv_type)
       ro_magicalize:
 	SvREADONLY_on(GvSV(gv));
       magicalize:
-	sv_magic(GvSV(gv), (SV*)gv, 0, name, len);
+	sv_magic(GvSV(gv), (SV*)gv, PERL_MAGIC_sv, name, len);
 	break;
 
     case '\014':	/* $^L */
@@ -1218,7 +1218,7 @@ Perl_Gv_AMupdate(pTHX_ HV *stash)
 {
   GV* gv;
   CV* cv;
-  MAGIC* mg=mg_find((SV*)stash,'c');
+  MAGIC* mg=mg_find((SV*)stash, PERL_MAGIC_overload_table);
   AMT *amtp = (mg) ? (AMT*)mg->mg_ptr: (AMT *) NULL;
   AMT amt;
   STRLEN n_a;
@@ -1226,7 +1226,7 @@ Perl_Gv_AMupdate(pTHX_ HV *stash)
   if (mg && amtp->was_ok_am == PL_amagic_generation
       && amtp->was_ok_sub == PL_sub_generation)
       return AMT_OVERLOADED(amtp);
-  sv_unmagic((SV*)stash, 'c');
+  sv_unmagic((SV*)stash, PERL_MAGIC_overload_table);
 
   DEBUG_o( Perl_deb(aTHX_ "Recalcing overload magic in package %s\n",HvNAME(stash)) );
 
@@ -1305,14 +1305,16 @@ Perl_Gv_AMupdate(pTHX_ HV *stash)
       AMT_AMAGIC_on(&amt);
       if (have_ovl)
 	  AMT_OVERLOADED_on(&amt);
-      sv_magic((SV*)stash, 0, 'c', (char*)&amt, sizeof(AMT));
+      sv_magic((SV*)stash, 0, PERL_MAGIC_overload_table,
+						(char*)&amt, sizeof(AMT));
       return have_ovl;
     }
   }
   /* Here we have no table: */
   /* no_table: */
   AMT_AMAGIC_off(&amt);
-  sv_magic((SV*)stash, 0, 'c', (char*)&amt, sizeof(AMTS));
+  sv_magic((SV*)stash, 0, PERL_MAGIC_overload_table,
+						(char*)&amt, sizeof(AMTS));
   return FALSE;
 }
 
@@ -1325,11 +1327,11 @@ Perl_gv_handler(pTHX_ HV *stash, I32 id)
 
     if (!stash)
         return Nullcv;
-    mg = mg_find((SV*)stash,'c');
+    mg = mg_find((SV*)stash, PERL_MAGIC_overload_table);
     if (!mg) {
       do_update:
 	Gv_AMupdate(stash);
-	mg = mg_find((SV*)stash,'c');
+	mg = mg_find((SV*)stash, PERL_MAGIC_overload_table);
     }
     amtp = (AMT*)mg->mg_ptr;
     if ( amtp->was_ok_am != PL_amagic_generation
@@ -1352,7 +1354,8 @@ Perl_amagic_call(pTHX_ SV *left, SV *right, int method, int flags)
   int postpr = 0, force_cpy = 0, assignshift = assign ? 1 : 0;
   HV* stash;
   if (!(AMGf_noleft & flags) && SvAMAGIC(left)
-      && (mg = mg_find((SV*)(stash=SvSTASH(SvRV(left))),'c'))
+      && (mg = mg_find((SV*)(stash=SvSTASH(SvRV(left))),
+			PERL_MAGIC_overload_table))
       && (ocvp = cvp = (AMT_AMAGIC((AMT*)mg->mg_ptr)
 			? (oamtp = amtp = (AMT*)mg->mg_ptr)->table
 			: (CV **) NULL))
@@ -1465,7 +1468,8 @@ Perl_amagic_call(pTHX_ SV *left, SV *right, int method, int flags)
 	 }
 	 if (!cv) goto not_found;
     } else if (!(AMGf_noright & flags) && SvAMAGIC(right)
-	       && (mg = mg_find((SV*)(stash=SvSTASH(SvRV(right))),'c'))
+	       && (mg = mg_find((SV*)(stash=SvSTASH(SvRV(right))),
+			PERL_MAGIC_overload_table))
 	       && (cvp = (AMT_AMAGIC((AMT*)mg->mg_ptr)
 			  ? (amtp = (AMT*)mg->mg_ptr)->table
 			  : (CV **) NULL))
diff --git a/hv.c b/hv.c
index 5df4dd882f..7058116511 100644
--- a/hv.c
+++ b/hv.c
@@ -163,14 +163,14 @@ Perl_hv_fetch(pTHX_ HV *hv, const char *key, I32 klen, I32 lval)
     }
 
     if (SvRMAGICAL(hv)) {
-	if (mg_find((SV*)hv,'P') || SvGMAGICAL((SV*)hv)) {
+	if (mg_find((SV*)hv, PERL_MAGIC_tied) || SvGMAGICAL((SV*)hv)) {
 	    sv = sv_newmortal();
 	    mg_copy((SV*)hv, sv, key, klen);
 	    PL_hv_fetch_sv = sv;
 	    return &PL_hv_fetch_sv;
 	}
 #ifdef ENV_IS_CASELESS
-	else if (mg_find((SV*)hv,'E')) {
+	else if (mg_find((SV*)hv, PERL_MAGIC_env)) {
 	    U32 i;
 	    for (i = 0; i < klen; ++i)
 		if (isLOWER(key[i])) {
@@ -283,7 +283,7 @@ Perl_hv_fetch_ent(pTHX_ HV *hv, SV *keysv, I32 lval, register U32 hash)
 	return 0;
 
     if (SvRMAGICAL(hv)) {
-	if (mg_find((SV*)hv,'P') || SvGMAGICAL((SV*)hv)) {
+	if (mg_find((SV*)hv, PERL_MAGIC_tied) || SvGMAGICAL((SV*)hv)) {
 	    sv = sv_newmortal();
 	    keysv = sv_2mortal(newSVsv(keysv));
 	    mg_copy((SV*)hv, sv, (char*)keysv, HEf_SVKEY);
@@ -297,7 +297,7 @@ Perl_hv_fetch_ent(pTHX_ HV *hv, SV *keysv, I32 lval, register U32 hash)
 	    return &PL_hv_fetch_ent_mh;
 	}
 #ifdef ENV_IS_CASELESS
-	else if (mg_find((SV*)hv,'E')) {
+	else if (mg_find((SV*)hv, PERL_MAGIC_env)) {
 	    U32 i;
 	    key = SvPV(keysv, klen);
 	    for (i = 0; i < klen; ++i)
@@ -379,8 +379,8 @@ S_hv_magic_check(pTHX_ HV *hv, bool *needs_copy, bool *needs_store)
 	if (isUPPER(mg->mg_type)) {
 	    *needs_copy = TRUE;
 	    switch (mg->mg_type) {
-	    case 'P':
-	    case 'S':
+	    case PERL_MAGIC_tied:
+	    case PERL_MAGIC_sig:
 		*needs_store = FALSE;
 	    }
 	}
@@ -434,7 +434,7 @@ Perl_hv_store(pTHX_ HV *hv, const char *key, I32 klen, SV *val, register U32 has
 	    if (!xhv->xhv_array && !needs_store)
 		return 0;
 #ifdef ENV_IS_CASELESS
-	    else if (mg_find((SV*)hv,'E')) {
+	    else if (mg_find((SV*)hv, PERL_MAGIC_env)) {
                 key = savepvn(key,klen);
 		key = strupr(key);
 		hash = 0;
@@ -545,7 +545,7 @@ Perl_hv_store_ent(pTHX_ HV *hv, SV *keysv, SV *val, register U32 hash)
  	    if (!xhv->xhv_array && !needs_store)
  		return Nullhe;
 #ifdef ENV_IS_CASELESS
-	    else if (mg_find((SV*)hv,'E')) {
+	    else if (mg_find((SV*)hv, PERL_MAGIC_env)) {
 		key = SvPV(keysv, klen);
 		keysv = sv_2mortal(newSVpvn(key,klen));
 		(void)strupr(SvPVX(keysv));
@@ -647,14 +647,15 @@ Perl_hv_delete(pTHX_ HV *hv, const char *key, I32 klen, I32 flags)
 	    sv = *svp;
 	    mg_clear(sv);
 	    if (!needs_store) {
-		if (mg_find(sv, 'p')) {
-		    sv_unmagic(sv, 'p');        /* No longer an element */
+		if (mg_find(sv, PERL_MAGIC_tiedelem)) {
+		    /* No longer an element */
+		    sv_unmagic(sv, PERL_MAGIC_tiedelem);
 		    return sv;
 		}
 		return Nullsv;          /* element cannot be deleted */
 	    }
 #ifdef ENV_IS_CASELESS
-	    else if (mg_find((SV*)hv,'E')) {
+	    else if (mg_find((SV*)hv, PERL_MAGIC_env)) {
 		sv = sv_2mortal(newSVpvn(key,klen));
 		key = strupr(SvPVX(sv));
 	    }
@@ -744,14 +745,15 @@ Perl_hv_delete_ent(pTHX_ HV *hv, SV *keysv, I32 flags, U32 hash)
 	    sv = HeVAL(entry);
 	    mg_clear(sv);
 	    if (!needs_store) {
-		if (mg_find(sv, 'p')) {
-		    sv_unmagic(sv, 'p');	/* No longer an element */
+		if (mg_find(sv, PERL_MAGIC_tiedelem)) {
+		    /* No longer an element */
+		    sv_unmagic(sv, PERL_MAGIC_tiedelem);
 		    return sv;
 		}		
 		return Nullsv;		/* element cannot be deleted */
 	    }
 #ifdef ENV_IS_CASELESS
-	    else if (mg_find((SV*)hv,'E')) {
+	    else if (mg_find((SV*)hv, PERL_MAGIC_env)) {
 		key = SvPV(keysv, klen);
 		keysv = sv_2mortal(newSVpvn(key,klen));
 		(void)strupr(SvPVX(keysv));
@@ -836,14 +838,14 @@ Perl_hv_exists(pTHX_ HV *hv, const char *key, I32 klen)
     }
 
     if (SvRMAGICAL(hv)) {
-	if (mg_find((SV*)hv,'P') || SvGMAGICAL((SV*)hv)) {
+	if (mg_find((SV*)hv, PERL_MAGIC_tied) || SvGMAGICAL((SV*)hv)) {
 	    sv = sv_newmortal();
 	    mg_copy((SV*)hv, sv, key, klen);
-	    magic_existspack(sv, mg_find(sv, 'p'));
+	    magic_existspack(sv, mg_find(sv, PERL_MAGIC_tiedelem));
 	    return SvTRUE(sv);
 	}
 #ifdef ENV_IS_CASELESS
-	else if (mg_find((SV*)hv,'E')) {
+	else if (mg_find((SV*)hv, PERL_MAGIC_env)) {
 	    sv = sv_2mortal(newSVpvn(key,klen));
 	    key = strupr(SvPVX(sv));
 	}
@@ -926,16 +928,16 @@ Perl_hv_exists_ent(pTHX_ HV *hv, SV *keysv, U32 hash)
 	return 0;
 
     if (SvRMAGICAL(hv)) {
-	if (mg_find((SV*)hv,'P') || SvGMAGICAL((SV*)hv)) {
+	if (mg_find((SV*)hv, PERL_MAGIC_tied) || SvGMAGICAL((SV*)hv)) {
            SV* svret = sv_newmortal();
 	    sv = sv_newmortal();
 	    keysv = sv_2mortal(newSVsv(keysv));
 	    mg_copy((SV*)hv, sv, (char*)keysv, HEf_SVKEY);
-           magic_existspack(svret, mg_find(sv, 'p'));
+           magic_existspack(svret, mg_find(sv, PERL_MAGIC_tiedelem));
            return SvTRUE(svret);
 	}
 #ifdef ENV_IS_CASELESS
-	else if (mg_find((SV*)hv,'E')) {
+	else if (mg_find((SV*)hv, PERL_MAGIC_env)) {
 	    key = SvPV(keysv, klen);
 	    keysv = sv_2mortal(newSVpvn(key,klen));
 	    (void)strupr(SvPVX(keysv));
@@ -1175,7 +1177,7 @@ Perl_newHVhv(pTHX_ HV *ohv)
 	return hv;
 
 #if 0
-    if (! SvTIED_mg((SV*)ohv, 'P')) {
+    if (! SvTIED_mg((SV*)ohv, PERL_MAGIC_tied)) {
 	/* Quick way ???*/
     }
     else
@@ -1381,7 +1383,7 @@ Perl_hv_iternext(pTHX_ HV *hv)
     xhv = (XPVHV*)SvANY(hv);
     oldentry = entry = xhv->xhv_eiter;
 
-    if ((mg = SvTIED_mg((SV*)hv, 'P'))) {
+    if ((mg = SvTIED_mg((SV*)hv, PERL_MAGIC_tied))) {
 	SV *key = sv_newmortal();
 	if (entry) {
 	    sv_setsv(key, HeSVKEY_force(entry));
@@ -1497,7 +1499,7 @@ SV *
 Perl_hv_iterval(pTHX_ HV *hv, register HE *entry)
 {
     if (SvRMAGICAL(hv)) {
-	if (mg_find((SV*)hv,'P')) {
+	if (mg_find((SV*)hv, PERL_MAGIC_tied)) {
 	    SV* sv = sv_newmortal();
 	    if (HeKLEN(entry) == HEf_SVKEY)
 		mg_copy((SV*)hv, sv, (char*)HeKEY_sv(entry), HEf_SVKEY);
diff --git a/mg.c b/mg.c
index de687c4c97..b68a52e1d2 100644
--- a/mg.c
+++ b/mg.c
@@ -286,8 +286,9 @@ Perl_mg_copy(pTHX_ SV *sv, SV *nsv, const char *key, I32 klen)
     for (mg = SvMAGIC(sv); mg; mg = mg->mg_moremagic) {
 	if (isUPPER(mg->mg_type)) {
 	    sv_magic(nsv,
-		     mg->mg_type == 'P' ? SvTIED_obj(sv, mg) :
-		     (mg->mg_type == 'D' && mg->mg_obj) ? sv : mg->mg_obj,
+		     mg->mg_type == PERL_MAGIC_tied ? SvTIED_obj(sv, mg) :
+		     (mg->mg_type == PERL_MAGIC_regdata && mg->mg_obj)
+							? sv : mg->mg_obj,
 		     toLOWER(mg->mg_type), key, klen);
 	    count++;
 	}
@@ -313,7 +314,7 @@ Perl_mg_free(pTHX_ SV *sv)
 	moremagic = mg->mg_moremagic;
 	if (vtbl && vtbl->svt_free)
 	    CALL_FPTR(vtbl->svt_free)(aTHX_ sv, mg);
-	if (mg->mg_ptr && mg->mg_type != 'g') {
+	if (mg->mg_ptr && mg->mg_type != PERL_MAGIC_regex_global) {
 	    if (mg->mg_len >= 0)
 		Safefree(mg->mg_ptr);
 	    else if (mg->mg_len == HEf_SVKEY)
@@ -1130,7 +1131,7 @@ Perl_magic_getnkeys(pTHX_ SV *sv, MAGIC *mg)
 
     if (hv) {
 	(void) hv_iterinit(hv);
-	if (! SvTIED_mg((SV*)hv, 'P'))
+	if (! SvTIED_mg((SV*)hv, PERL_MAGIC_tied))
 	    i = HvKEYS(hv);
 	else {
 	    /*SUPPRESS 560*/
@@ -1169,7 +1170,7 @@ S_magic_methcall(pTHX_ SV *sv, MAGIC *mg, char *meth, I32 flags, int n, SV *val)
 	    else if (mg->mg_len == HEf_SVKEY)
 		PUSHs((SV*)mg->mg_ptr);
 	}
-	else if (mg->mg_type == 'p') {
+	else if (mg->mg_type == PERL_MAGIC_tiedelem) {
 	    PUSHs(sv_2mortal(newSViv(mg->mg_len)));
 	}
     }
@@ -1332,7 +1333,7 @@ Perl_magic_getpos(pTHX_ SV *sv, MAGIC *mg)
     SV* lsv = LvTARG(sv);
 
     if (SvTYPE(lsv) >= SVt_PVMG && SvMAGIC(lsv)) {
-	mg = mg_find(lsv, 'g');
+	mg = mg_find(lsv, PERL_MAGIC_regex_global);
 	if (mg && mg->mg_len >= 0) {
 	    I32 i = mg->mg_len;
 	    if (DO_UTF8(lsv))
@@ -1356,12 +1357,12 @@ Perl_magic_setpos(pTHX_ SV *sv, MAGIC *mg)
     mg = 0;
 
     if (SvTYPE(lsv) >= SVt_PVMG && SvMAGIC(lsv))
-	mg = mg_find(lsv, 'g');
+	mg = mg_find(lsv, PERL_MAGIC_regex_global);
     if (!mg) {
 	if (!SvOK(sv))
 	    return 0;
-	sv_magic(lsv, (SV*)0, 'g', Nullch, 0);
-	mg = mg_find(lsv, 'g');
+	sv_magic(lsv, (SV*)0, PERL_MAGIC_regex_global, Nullch, 0);
+	mg = mg_find(lsv, PERL_MAGIC_regex_global);
     }
     else if (!SvOK(sv)) {
 	mg->mg_len = -1;
@@ -1581,7 +1582,7 @@ Perl_vivify_defelem(pTHX_ SV *sv)
     MAGIC *mg;
     SV *value = Nullsv;
 
-    if (!LvTARGLEN(sv) || !(mg = mg_find(sv, 'y')))
+    if (!LvTARGLEN(sv) || !(mg = mg_find(sv, PERL_MAGIC_defelem)))
 	return;
     if (mg->mg_obj) {
 	SV *ahv = LvTARG(sv);
@@ -1650,7 +1651,7 @@ Perl_magic_setmglob(pTHX_ SV *sv, MAGIC *mg)
 int
 Perl_magic_setbm(pTHX_ SV *sv, MAGIC *mg)
 {
-    sv_unmagic(sv, 'B');
+    sv_unmagic(sv, PERL_MAGIC_bm);
     SvVALID_off(sv);
     return 0;
 }
@@ -1658,7 +1659,7 @@ Perl_magic_setbm(pTHX_ SV *sv, MAGIC *mg)
 int
 Perl_magic_setfm(pTHX_ SV *sv, MAGIC *mg)
 {
-    sv_unmagic(sv, 'f');
+    sv_unmagic(sv, PERL_MAGIC_fm);
     SvCOMPILED_off(sv);
     return 0;
 }
diff --git a/op.c b/op.c
index 5a51f9b83c..61f485073a 100644
--- a/op.c
+++ b/op.c
@@ -643,7 +643,7 @@ Perl_find_threadsv(pTHX_ const char *name)
 	    break;
 	case ';':
 	    sv_setpv(sv, "\034");
-	    sv_magic(sv, 0, 0, name, 1);
+	    sv_magic(sv, 0, PERL_MAGIC_sv, name, 1);
 	    break;
 	case '&':
 	case '`':
@@ -667,7 +667,7 @@ Perl_find_threadsv(pTHX_ const char *name)
 	/* case '!': */
 
 	default:
-	    sv_magic(sv, 0, 0, name, 1);
+	    sv_magic(sv, 0, PERL_MAGIC_sv, name, 1);
 	}
 	DEBUG_S(PerlIO_printf(Perl_error_log,
 			      "find_threadsv: new SV %p for $%s%c\n",
diff --git a/perl.c b/perl.c
index 64aa4c9101..2e39794f14 100644
--- a/perl.c
+++ b/perl.c
@@ -788,7 +788,8 @@ perl_destruct(pTHXx)
 	    MAGIC* moremagic;
 	    for (mg = SvMAGIC(PL_mess_sv); mg; mg = moremagic) {
 		moremagic = mg->mg_moremagic;
-		if (mg->mg_ptr && mg->mg_type != 'g' && mg->mg_len >= 0)
+		if (mg->mg_ptr && mg->mg_type != PERL_MAGIC_regex_global
+						&& mg->mg_len >= 0)
 		    Safefree(mg->mg_ptr);
 		Safefree(mg);
 	    }
@@ -2013,7 +2014,7 @@ Perl_magicname(pTHX_ char *sym, char *name, I32 namlen)
     register GV *gv;
 
     if ((gv = gv_fetchpv(sym,TRUE, SVt_PV)))
-	sv_magic(GvSV(gv), (SV*)gv, 0, name, namlen);
+	sv_magic(GvSV(gv), (SV*)gv, PERL_MAGIC_sv, name, namlen);
 }
 
 STATIC void
@@ -3377,7 +3378,7 @@ S_init_postdump_symbols(pTHX_ register int argc, register char **argv, register
 	HV *hv;
 	GvMULTI_on(PL_envgv);
 	hv = GvHVn(PL_envgv);
-	hv_magic(hv, Nullgv, 'E');
+	hv_magic(hv, Nullgv, PERL_MAGIC_env);
 #ifdef USE_ENVIRON_ARRAY
 	/* Note that if the supplied env parameter is actually a copy
 	   of the global environ then it may now point to free'd memory
diff --git a/perl.h b/perl.h
index 9f135b109c..f14f897bdf 100644
--- a/perl.h
+++ b/perl.h
@@ -2300,6 +2300,52 @@ Gid_t getegid (void);
 #endif /* DEBUGGING */
 
 
+/* These constants should be used in preference to to raw characters
+ * when using magic. Note that some perl guts still assume
+ * certain character properties of these constants, namely that
+ * isUPPER() and toLOWER() may do useful mappings.
+ *
+ * Update the magic_names table in dump.c when adding/amending these
+ */
+
+#define PERL_MAGIC_sv		  '\0' /* Special scalar variable */
+#define PERL_MAGIC_overload	  'A' /* %OVERLOAD hash */
+#define PERL_MAGIC_overload_elem  'a' /* %OVERLOAD hash element */
+#define PERL_MAGIC_overload_table 'c' /* Holds overload table (AMT) on stash */
+#define PERL_MAGIC_bm		  'B' /* Boyer-Moore (fast string search) */
+#define PERL_MAGIC_regdata	  'D' /* Regex match position data
+					(@+ and @- vars) */
+#define PERL_MAGIC_regdatum	  'd' /* Regex match position data element */
+#define PERL_MAGIC_env		  'E' /* %ENV hash */
+#define PERL_MAGIC_envelem	  'e' /* %ENV hash element */
+#define PERL_MAGIC_fm		  'f' /* Formline ('compiled' format) */
+#define PERL_MAGIC_regex_global	  'g' /* m//g target / study()ed string */
+#define PERL_MAGIC_isa		  'I' /* @ISA array */
+#define PERL_MAGIC_isaelem	  'i' /* @ISA array element */
+#define PERL_MAGIC_nkeys	  'k' /* scalar(keys()) lvalue */
+#define PERL_MAGIC_dbfile	  'L' /* Debugger %_<filename */
+#define PERL_MAGIC_dbline	  'l' /* Debugger %_<filename element */
+#define PERL_MAGIC_mutex	  'm' /* ??? */
+#define PERL_MAGIC_collxfrm	  'o' /* Locale transformation */
+#define PERL_MAGIC_tied		  'P' /* Tied array or hash */
+#define PERL_MAGIC_tiedelem	  'p' /* Tied array or hash element */
+#define PERL_MAGIC_tiedscalar	  'q' /* Tied scalar or handle */
+#define PERL_MAGIC_qr		  'r' /* precompiled qr// regex */
+#define PERL_MAGIC_sig		  'S' /* %SIG hash */
+#define PERL_MAGIC_sigelem	  's' /* %SIG hash element */
+#define PERL_MAGIC_taint	  't' /* Taintedness */
+#define PERL_MAGIC_uvar		  'U' /* Available for use by extensions */
+#define PERL_MAGIC_vec		  'v' /* vec() lvalue */
+#define PERL_MAGIC_substr	  'x' /* substr() lvalue */
+#define PERL_MAGIC_defelem	  'y' /* Shadow "foreach" iterator variable /
+					smart parameter vivification */
+#define PERL_MAGIC_glob		  '*' /* GV (typeglob) */
+#define PERL_MAGIC_arylen	  '#' /* Array length ($#ary) */
+#define PERL_MAGIC_pos		  '.' /* pos() lvalue */
+#define PERL_MAGIC_backref	  '<' /* ??? */
+#define PERL_MAGIC_ext		  '~' /* Available for use by extensions */
+
+
 #define YYMAXDEPTH 300
 
 #ifndef assert  /* <assert.h> might have been included somehow */
@@ -2317,7 +2363,7 @@ struct ufuncs {
     IV uf_index;
 };
 
-/* In pre-5.7-Perls the 'U' magic didn't get the thread context.
+/* In pre-5.7-Perls the PERL_MAGIC_uvar magic didn't get the thread context.
  * XS code wanting to be backward compatible can do something
  * like the following:
 
diff --git a/perlio.c b/perlio.c
index ba932f3d69..bf628b2377 100644
--- a/perlio.c
+++ b/perlio.c
@@ -451,9 +451,9 @@ XS(XS_io_MODIFY_SCALAR_ATTRIBUTES)
  MAGIC *mg;
  int count = 0;
  int i;
- sv_magic(sv, (SV *)av, '~', NULL, 0);
+ sv_magic(sv, (SV *)av, PERL_MAGIC_ext, NULL, 0);
  SvRMAGICAL_off(sv);
- mg = mg_find(sv,'~');
+ mg = mg_find(sv, PERL_MAGIC_ext);
  mg->mg_virtual = &perlio_vtab;
  mg_magical(sv);
  Perl_warn(aTHX_ "attrib %"SVf,sv);
diff --git a/pod/perlguts.pod b/pod/perlguts.pod
index 3b10af9eee..4a06489467 100644
--- a/pod/perlguts.pod
+++ b/pod/perlguts.pod
@@ -810,13 +810,17 @@ copy of the name is stored in C<mg_ptr> field.
 The sv_magic function uses C<how> to determine which, if any, predefined
 "Magic Virtual Table" should be assigned to the C<mg_virtual> field.
 See the "Magic Virtual Table" section below.  The C<how> argument is also
-stored in the C<mg_type> field.
+stored in the C<mg_type> field. The value of C<how> should be chosen
+from the set of macros C<PERL_MAGIC_foo> found perl.h. Note that before
+these macros were added, perl internals used to directly use character
+literals, so you may occasionally come across old code or documentation
+referrring to 'U' magic rather than C<PERL_MAGIC_uvar> for example.
 
 The C<obj> argument is stored in the C<mg_obj> field of the C<MAGIC>
 structure.  If it is not the same as the C<sv> argument, the reference
 count of the C<obj> object is incremented.  If it is the same, or if
-the C<how> argument is "#", or if it is a NULL pointer, then C<obj> is
-merely stored, without the reference count being incremented.
+the C<how> argument is C<PERL_MAGIC_arylen>", or if it is a NULL pointer,
+then C<obj> is merely stored, without the reference count being incremented.
 
 There is also a function to add magic to an C<HV>:
 
@@ -860,67 +864,76 @@ actions depending on which function is being called.
     svt_free            Free any extra storage associated with the SV.
 
 For instance, the MGVTBL structure called C<vtbl_sv> (which corresponds
-to an C<mg_type> of '\0') contains:
+to an C<mg_type> of C<PERL_MAGIC_sv>) contains:
 
     { magic_get, magic_set, magic_len, 0, 0 }
 
-Thus, when an SV is determined to be magical and of type '\0', if a get
-operation is being performed, the routine C<magic_get> is called.  All
-the various routines for the various magical types begin with C<magic_>.
-NOTE: the magic routines are not considered part of the Perl API, and may
-not be exported by the Perl library.
+Thus, when an SV is determined to be magical and of type C<PERL_MAGIC_sv>,
+if a get operation is being performed, the routine C<magic_get> is
+called.  All the various routines for the various magical types begin
+with C<magic_>.  NOTE: the magic routines are not considered part of
+the Perl API, and may not be exported by the Perl library.
 
 The current kinds of Magic Virtual Tables are:
 
-    mg_type  MGVTBL              Type of magic
-    -------  ------              ----------------------------
-    \0       vtbl_sv             Special scalar variable
-    A        vtbl_amagic         %OVERLOAD hash
-    a        vtbl_amagicelem     %OVERLOAD hash element
-    c        (none)              Holds overload table (AMT) on stash
-    B        vtbl_bm             Boyer-Moore (fast string search)
-    D        vtbl_regdata        Regex match position data (@+ and @- vars)
-    d        vtbl_regdatum       Regex match position data element
-    E        vtbl_env            %ENV hash
-    e        vtbl_envelem        %ENV hash element
-    f        vtbl_fm             Formline ('compiled' format)
-    g        vtbl_mglob          m//g target / study()ed string
-    I        vtbl_isa            @ISA array
-    i        vtbl_isaelem        @ISA array element
-    k        vtbl_nkeys          scalar(keys()) lvalue
-    L        (none)              Debugger %_<filename 
-    l        vtbl_dbline         Debugger %_<filename element
-    o        vtbl_collxfrm       Locale transformation
-    P        vtbl_pack           Tied array or hash
-    p        vtbl_packelem       Tied array or hash element
-    q        vtbl_packelem       Tied scalar or handle
-    S        vtbl_sig            %SIG hash
-    s        vtbl_sigelem        %SIG hash element
-    t        vtbl_taint          Taintedness
-    U        vtbl_uvar           Available for use by extensions
-    v        vtbl_vec            vec() lvalue
-    x        vtbl_substr         substr() lvalue
-    y        vtbl_defelem        Shadow "foreach" iterator variable /
-                                  smart parameter vivification
-    *        vtbl_glob           GV (typeglob)
-    #        vtbl_arylen         Array length ($#ary)
-    .        vtbl_pos            pos() lvalue
-    ~        (none)              Available for use by extensions
+    mg_type
+    (old-style char and macro)   MGVTBL         Type of magic
+    --------------------------   ------         ----------------------------
+    \0 PERL_MAGIC_sv             vtbl_sv        Special scalar variable
+    A  PERL_MAGIC_overload       vtbl_amagic    %OVERLOAD hash
+    a  PERL_MAGIC_overload_elem  vtbl_amagicelem %OVERLOAD hash element
+    c  PERL_MAGIC_overload_table (none)         Holds overload table (AMT)
+						on stash
+    B  PERL_MAGIC_bm             vtbl_bm        Boyer-Moore (fast string search)
+    D  PERL_MAGIC_regdata        vtbl_regdata   Regex match position data
+						(@+ and @- vars)
+    d  PERL_MAGIC_regdatum       vtbl_regdatum  Regex match position data
+						element
+    E  PERL_MAGIC_env            vtbl_env       %ENV hash
+    e  PERL_MAGIC_envelem        vtbl_envelem   %ENV hash element
+    f  PERL_MAGIC_fm             vtbl_fm        Formline ('compiled' format)
+    g  PERL_MAGIC_regex_global   vtbl_mglob     m//g target / study()ed string
+    I  PERL_MAGIC_isa            vtbl_isa       @ISA array
+    i  PERL_MAGIC_isaelem        vtbl_isaelem   @ISA array element
+    k  PERL_MAGIC_nkeys          vtbl_nkeys     scalar(keys()) lvalue
+    L  PERL_MAGIC_dbfile         (none)         Debugger %_<filename
+    l  PERL_MAGIC_dbline         vtbl_dbline    Debugger %_<filename element
+    m  PERL_MAGIC_mutex          vtbl_mutex     ???
+    o  PERL_MAGIC_collxfrm       vtbl_collxfrm  Locale transformation
+    P  PERL_MAGIC_tied           vtbl_pack      Tied array or hash
+    p  PERL_MAGIC_tiedelem       vtbl_packelem  Tied array or hash element
+    q  PERL_MAGIC_tiedscalar     vtbl_packelem  Tied scalar or handle
+    r  PERL_MAGIC_qr             vtbl_qr        precompiled qr// regex
+    S  PERL_MAGIC_sig            vtbl_sig       %SIG hash
+    s  PERL_MAGIC_sigelem        vtbl_sigelem   %SIG hash element
+    t  PERL_MAGIC_taint          vtbl_taint     Taintedness
+    U  PERL_MAGIC_uvar           vtbl_uvar      Available for use by extensions
+    v  PERL_MAGIC_vec            vtbl_vec       vec() lvalue
+    x  PERL_MAGIC_substr         vtbl_substr    substr() lvalue
+    y  PERL_MAGIC_defelem        vtbl_defelem   Shadow "foreach" iterator
+						variable / smart parameter
+						vivification
+    *  PERL_MAGIC_glob           vtbl_glob      GV (typeglob)
+    #  PERL_MAGIC_arylen         vtbl_arylen    Array length ($#ary)
+    .  PERL_MAGIC_pos            vtbl_pos       pos() lvalue
+    <  PERL_MAGIC_backref        vtbl_backref   ???
+    ~  PERL_MAGIC_ext            (none)         Available for use by extensions
 
 When an uppercase and lowercase letter both exist in the table, then the
 uppercase letter is used to represent some kind of composite type (a list
 or a hash), and the lowercase letter is used to represent an element of
-that composite type.
-
-The '~' and 'U' magic types are defined specifically for use by
-extensions and will not be used by perl itself.  Extensions can use
-'~' magic to 'attach' private information to variables (typically
-objects).  This is especially useful because there is no way for
-normal perl code to corrupt this private information (unlike using
-extra elements of a hash object).
-
-Similarly, 'U' magic can be used much like tie() to call a C function
-any time a scalar's value is used or changed.  The C<MAGIC>'s
+that composite type. Some internals code makes use of this case
+relationship.
+
+The C<PERL_MAGIC_ext> and C<PERL_MAGIC_uvar> magic types are defined
+specifically for use by extensions and will not be used by perl itself.
+Extensions can use C<PERL_MAGIC_ext> magic to 'attach' private information
+to variables (typically objects).  This is especially useful because
+there is no way for normal perl code to corrupt this private information
+(unlike using extra elements of a hash object).
+
+Similarly, C<PERL_MAGIC_uvar> magic can be used much like tie() to call a
+C function any time a scalar's value is used or changed.  The C<MAGIC>'s
 C<mg_ptr> field points to a C<ufuncs> structure:
 
     struct ufuncs {
@@ -930,8 +943,8 @@ C<mg_ptr> field points to a C<ufuncs> structure:
     };
 
 When the SV is read from or written to, the C<uf_val> or C<uf_set>
-function will be called with C<uf_index> as the first arg and a
-pointer to the SV as the second.  A simple example of how to add 'U'
+function will be called with C<uf_index> as the first arg and a pointer to
+the SV as the second.  A simple example of how to add C<PERL_MAGIC_uvar>
 magic is shown below.  Note that the ufuncs structure is copied by
 sv_magic, so you can safely allocate it on the stack.
 
@@ -944,14 +957,14 @@ sv_magic, so you can safely allocate it on the stack.
         uf.uf_val   = &my_get_fn;
         uf.uf_set   = &my_set_fn;
         uf.uf_index = 0;
-        sv_magic(sv, 0, 'U', (char*)&uf, sizeof(uf));
+        sv_magic(sv, 0, PERL_MAGIC_uvar, (char*)&uf, sizeof(uf));
 
-Note that because multiple extensions may be using '~' or 'U' magic,
-it is important for extensions to take extra care to avoid conflict.
-Typically only using the magic on objects blessed into the same class
-as the extension is sufficient.  For '~' magic, it may also be
-appropriate to add an I32 'signature' at the top of the private data
-area and check that.
+Note that because multiple extensions may be using C<PERL_MAGIC_ext>
+or C<PERL_MAGIC_uvar> magic, it is important for extensions to take
+extra care to avoid conflict.  Typically only using the magic on
+objects blessed into the same class as the extension is sufficient.
+For C<PERL_MAGIC_ext> magic, it may also be appropriate to add an I32
+'signature' at the top of the private data area and check that.
 
 Also note that the C<sv_set*()> and C<sv_cat*()> functions described
 earlier do B<not> invoke 'set' magic on their targets.  This must
@@ -981,7 +994,8 @@ the mg_type field is changed to be the lowercase letter.
 
 =head2 Understanding the Magic of Tied Hashes and Arrays
 
-Tied hashes and arrays are magical beasts of the 'P' magic type.
+Tied hashes and arrays are magical beasts of the C<PERL_MAGIC_tied>
+magic type.
 
 WARNING: As of the 5.004 release, proper usage of the array and hash
 access functions requires understanding a few caveats.  Some
@@ -1012,7 +1026,7 @@ to do this.
         tie = newRV_noinc((SV*)newHV());
         stash = gv_stashpv("MyTie", TRUE);
         sv_bless(tie, stash);
-        hv_magic(hash, tie, 'P');
+        hv_magic(hash, tie, PERL_MAGIC_tied);
         RETVAL = newRV_noinc(hash);
     OUTPUT:
         RETVAL
diff --git a/pp.c b/pp.c
index d68b689745..c265e9541b 100644
--- a/pp.c
+++ b/pp.c
@@ -341,7 +341,7 @@ PP(pp_av2arylen)
     if (!sv) {
 	AvARYLEN(av) = sv = NEWSV(0,0);
 	sv_upgrade(sv, SVt_IV);
-	sv_magic(sv, (SV*)av, '#', Nullch, 0);
+	sv_magic(sv, (SV*)av, PERL_MAGIC_arylen, Nullch, 0);
     }
     SETs(sv);
     RETURN;
@@ -354,7 +354,7 @@ PP(pp_pos)
     if (PL_op->op_flags & OPf_MOD || LVRET) {
 	if (SvTYPE(TARG) < SVt_PVLV) {
 	    sv_upgrade(TARG, SVt_PVLV);
-	    sv_magic(TARG, Nullsv, '.', Nullch, 0);
+	    sv_magic(TARG, Nullsv, PERL_MAGIC_pos, Nullch, 0);
 	}
 
 	LvTYPE(TARG) = '.';
@@ -370,7 +370,7 @@ PP(pp_pos)
 	MAGIC* mg;
 
 	if (SvTYPE(sv) >= SVt_PVMG && SvMAGIC(sv)) {
-	    mg = mg_find(sv, 'g');
+	    mg = mg_find(sv, PERL_MAGIC_regex_global);
 	    if (mg && mg->mg_len >= 0) {
 		I32 i = mg->mg_len;
 		if (DO_UTF8(sv))
@@ -715,7 +715,8 @@ PP(pp_study)
     }
 
     SvSCREAM_on(sv);
-    sv_magic(sv, Nullsv, 'g', Nullch, 0);	/* piggyback on m//g magic */
+    /* piggyback on m//g magic */
+    sv_magic(sv, Nullsv, PERL_MAGIC_regex_global, Nullch, 0);
     RETPUSHYES;
 }
 
@@ -783,11 +784,13 @@ PP(pp_defined)
 	RETPUSHNO;
     switch (SvTYPE(sv)) {
     case SVt_PVAV:
-	if (AvMAX(sv) >= 0 || SvGMAGICAL(sv) || (SvRMAGICAL(sv) && mg_find(sv,'P')))
+	if (AvMAX(sv) >= 0 || SvGMAGICAL(sv)
+		|| (SvRMAGICAL(sv) && mg_find(sv, PERL_MAGIC_tied)))
 	    RETPUSHYES;
 	break;
     case SVt_PVHV:
-	if (HvARRAY(sv) || SvGMAGICAL(sv) || (SvRMAGICAL(sv) && mg_find(sv,'P')))
+	if (HvARRAY(sv) || SvGMAGICAL(sv)
+		|| (SvRMAGICAL(sv) && mg_find(sv, PERL_MAGIC_tied)))
 	    RETPUSHYES;
 	break;
     case SVt_PVCV:
@@ -2809,7 +2812,7 @@ PP(pp_substr)
 	tmps += pos;
 	sv_setpvn(TARG, tmps, rem);
 #ifdef USE_LOCALE_COLLATE
-	sv_unmagic(TARG, 'o');
+	sv_unmagic(TARG, PERL_MAGIC_collxfrm);
 #endif
 	if (utf8_curlen)
 	    SvUTF8_on(TARG);
@@ -2845,7 +2848,7 @@ PP(pp_substr)
 
 	    if (SvTYPE(TARG) < SVt_PVLV) {
 		sv_upgrade(TARG, SVt_PVLV);
-		sv_magic(TARG, Nullsv, 'x', Nullch, 0);
+		sv_magic(TARG, Nullsv, PERL_MAGIC_substr, Nullch, 0);
 	    }
 
 	    LvTYPE(TARG) = 'x';
@@ -2875,7 +2878,7 @@ PP(pp_vec)
     if (lvalue) {			/* it's an lvalue! */
 	if (SvTYPE(TARG) < SVt_PVLV) {
 	    sv_upgrade(TARG, SVt_PVLV);
-	    sv_magic(TARG, Nullsv, 'v', Nullch, 0);
+	    sv_magic(TARG, Nullsv, PERL_MAGIC_vec, Nullch, 0);
 	}
 	LvTYPE(TARG) = 'v';
 	if (LvTARG(TARG) != src) {
@@ -3710,7 +3713,7 @@ PP(pp_splice)
     SV **tmparyval = 0;
     MAGIC *mg;
 
-    if ((mg = SvTIED_mg((SV*)ary, 'P'))) {
+    if ((mg = SvTIED_mg((SV*)ary, PERL_MAGIC_tied))) {
 	*MARK-- = SvTIED_obj((SV*)ary, mg);
 	PUSHMARK(MARK);
 	PUTBACK;
@@ -3904,7 +3907,7 @@ PP(pp_push)
     register SV *sv = &PL_sv_undef;
     MAGIC *mg;
 
-    if ((mg = SvTIED_mg((SV*)ary, 'P'))) {
+    if ((mg = SvTIED_mg((SV*)ary, PERL_MAGIC_tied))) {
 	*MARK-- = SvTIED_obj((SV*)ary, mg);
 	PUSHMARK(MARK);
 	PUTBACK;
@@ -3960,7 +3963,7 @@ PP(pp_unshift)
     register I32 i = 0;
     MAGIC *mg;
 
-    if ((mg = SvTIED_mg((SV*)ary, 'P'))) {
+    if ((mg = SvTIED_mg((SV*)ary, PERL_MAGIC_tied))) {
 	*MARK-- = SvTIED_obj((SV*)ary, mg);
 	PUSHMARK(MARK);
 	PUTBACK;
@@ -5843,7 +5846,7 @@ PP(pp_split)
 	av_extend(ary,0);
 	av_clear(ary);
 	SPAGAIN;
-	if ((mg = SvTIED_mg((SV*)ary, 'P'))) {
+	if ((mg = SvTIED_mg((SV*)ary, PERL_MAGIC_tied))) {
 	    PUSHMARK(SP);
 	    XPUSHs(SvTIED_obj((SV*)ary, mg));
 	}
@@ -6090,7 +6093,7 @@ PP(pp_split)
 void
 Perl_unlock_condpair(pTHX_ void *svv)
 {
-    MAGIC *mg = mg_find((SV*)svv, 'm');
+    MAGIC *mg = mg_find((SV*)svv, PERL_MAGIC_mutex);
 
     if (!mg)
 	Perl_croak(aTHX_ "panic: unlock_condpair unlocking non-mutex");
diff --git a/pp_ctl.c b/pp_ctl.c
index 166d1daabf..8e12e2b52c 100644
--- a/pp_ctl.c
+++ b/pp_ctl.c
@@ -91,7 +91,7 @@ PP(pp_regcomp)
     if (SvROK(tmpstr)) {
 	SV *sv = SvRV(tmpstr);
 	if(SvMAGICAL(sv))
-	    mg = mg_find(sv, 'r');
+	    mg = mg_find(sv, PERL_MAGIC_qr);
     }
     if (mg) {
 	regexp *re = (regexp *)mg->mg_obj;
@@ -227,9 +227,9 @@ PP(pp_substcont)
 	I32 i;
 	if (SvTYPE(sv) < SVt_PVMG)
 	    (void)SvUPGRADE(sv, SVt_PVMG);
-	if (!(mg = mg_find(sv, 'g'))) {
-	    sv_magic(sv, Nullsv, 'g', Nullch, 0);
-	    mg = mg_find(sv, 'g');
+	if (!(mg = mg_find(sv, PERL_MAGIC_regex_global))) {
+	    sv_magic(sv, Nullsv, PERL_MAGIC_regex_global, Nullch, 0);
+	    mg = mg_find(sv, PERL_MAGIC_regex_global);
 	}
 	i = m - orig;
 	if (DO_UTF8(sv))
@@ -3779,7 +3779,7 @@ S_doparseform(pTHX_ SV *sv)
     }
     Copy(fops, s, arg, U16);
     Safefree(fops);
-    sv_magic(sv, Nullsv, 'f', Nullch, 0);
+    sv_magic(sv, Nullsv, PERL_MAGIC_fm, Nullch, 0);
     SvCOMPILED_on(sv);
 }
 
diff --git a/pp_hot.c b/pp_hot.c
index 9e484fca88..1c0c417161 100644
--- a/pp_hot.c
+++ b/pp_hot.c
@@ -553,7 +553,7 @@ PP(pp_print)
 	gv = (GV*)*++MARK;
     else
 	gv = PL_defoutgv;
-    if ((mg = SvTIED_mg((SV*)gv, 'q'))) {
+    if ((mg = SvTIED_mg((SV*)gv, PERL_MAGIC_tiedscalar))) {
       had_magic:
 	if (MARK == ORIGMARK) {
 	    /* If using default handle then we need to make space to
@@ -577,7 +577,8 @@ PP(pp_print)
 	RETURN;
     }
     if (!(io = GvIO(gv))) {
-        if ((GvEGV(gv)) && (mg = SvTIED_mg((SV*)GvEGV(gv),'q')))
+        if ((GvEGV(gv))
+		&& (mg = SvTIED_mg((SV*)GvEGV(gv), PERL_MAGIC_tiedscalar)))
             goto had_magic;
 	if (ckWARN2(WARN_UNOPENED,WARN_CLOSED))
 	    report_evil_fh(gv, io, PL_op->op_type);
@@ -1184,7 +1185,7 @@ PP(pp_qr)
     register PMOP *pm = cPMOP;
     SV *rv = sv_newmortal();
     SV *sv = newSVrv(rv, "Regexp");
-    sv_magic(sv,(SV*)ReREFCNT_inc(pm->op_pmregexp),'r',0,0);
+    sv_magic(sv,(SV*)ReREFCNT_inc(pm->op_pmregexp), PERL_MAGIC_qr,0,0);
     RETURNX(PUSHs(rv));
 }
 
@@ -1242,7 +1243,7 @@ PP(pp_match)
     if ((global = pm->op_pmflags & PMf_GLOBAL)) {
 	rx->startp[0] = -1;
 	if (SvTYPE(TARG) >= SVt_PVMG && SvMAGIC(TARG)) {
-	    MAGIC* mg = mg_find(TARG, 'g');
+	    MAGIC* mg = mg_find(TARG, PERL_MAGIC_regex_global);
 	    if (mg && mg->mg_len >= 0) {
 		if (!(rx->reganch & ROPT_GPOS_SEEN))
 		    rx->endp[0] = rx->startp[0] = mg->mg_len;
@@ -1342,10 +1343,10 @@ play_it_again:
 	if (global) {
 	    MAGIC* mg = 0;
 	    if (SvTYPE(TARG) >= SVt_PVMG && SvMAGIC(TARG))
-		mg = mg_find(TARG, 'g');
+		mg = mg_find(TARG, PERL_MAGIC_regex_global);
 	    if (!mg) {
-		sv_magic(TARG, (SV*)0, 'g', Nullch, 0);
-		mg = mg_find(TARG, 'g');
+		sv_magic(TARG, (SV*)0, PERL_MAGIC_regex_global, Nullch, 0);
+		mg = mg_find(TARG, PERL_MAGIC_regex_global);
 	    }
 	    if (rx->startp[0] != -1) {
 		mg->mg_len = rx->endp[0];
@@ -1404,7 +1405,7 @@ nope:
 ret_no:
     if (global && !(pm->op_pmflags & PMf_CONTINUE)) {
 	if (SvTYPE(TARG) >= SVt_PVMG && SvMAGIC(TARG)) {
-	    MAGIC* mg = mg_find(TARG, 'g');
+	    MAGIC* mg = mg_find(TARG, PERL_MAGIC_regex_global);
 	    if (mg)
 		mg->mg_len = -1;
 	}
@@ -1428,7 +1429,7 @@ Perl_do_readline(pTHX)
     I32 gimme = GIMME_V;
     MAGIC *mg;
 
-    if ((mg = SvTIED_mg((SV*)PL_last_in_gv, 'q'))) {
+    if ((mg = SvTIED_mg((SV*)PL_last_in_gv, PERL_MAGIC_tiedscalar))) {
 	PUSHMARK(SP);
 	XPUSHs(SvTIED_obj((SV*)PL_last_in_gv, mg));
 	PUTBACK;
@@ -1649,7 +1650,7 @@ PP(pp_helem)
 	    lv = sv_newmortal();
 	    sv_upgrade(lv, SVt_PVLV);
 	    LvTYPE(lv) = 'y';
-	    sv_magic(lv, key2 = newSVsv(keysv), 'y', Nullch, 0);
+	    sv_magic(lv, key2 = newSVsv(keysv), PERL_MAGIC_defelem, Nullch, 0);
 	    SvREFCNT_dec(key2);	/* sv_magic() increments refcount */
 	    LvTARG(lv) = SvREFCNT_inc(hv);
 	    LvTARGLEN(lv) = 1;
@@ -1838,7 +1839,7 @@ PP(pp_iter)
 	    lv = cx->blk_loop.iterlval = NEWSV(26, 0);
 	    sv_upgrade(lv, SVt_PVLV);
 	    LvTYPE(lv) = 'y';
-	    sv_magic(lv, Nullsv, 'y', Nullch, 0);
+	    sv_magic(lv, Nullsv, PERL_MAGIC_defelem, Nullch, 0);
 	}
 	LvTARG(lv) = SvREFCNT_inc(av);
 	LvTARGOFF(lv) = cx->blk_loop.iterix;
@@ -2899,7 +2900,7 @@ PP(pp_aelem)
 	    lv = sv_newmortal();
 	    sv_upgrade(lv, SVt_PVLV);
 	    LvTYPE(lv) = 'y';
-	    sv_magic(lv, Nullsv, 'y', Nullch, 0);
+	    sv_magic(lv, Nullsv, PERL_MAGIC_defelem, Nullch, 0);
 	    LvTARG(lv) = SvREFCNT_inc(av);
 	    LvTARGOFF(lv) = elem;
 	    LvTARGLEN(lv) = 1;
diff --git a/pp_sys.c b/pp_sys.c
index 826a5888e2..ed5963804a 100644
--- a/pp_sys.c
+++ b/pp_sys.c
@@ -510,7 +510,7 @@ PP(pp_open)
     if (GvIOp(gv))
 	IoFLAGS(GvIOp(gv)) &= ~IOf_UNTAINT;
 
-    if ((mg = SvTIED_mg((SV*)gv, 'q'))) {
+    if ((mg = SvTIED_mg((SV*)gv, PERL_MAGIC_tiedscalar))) {
 	/* Method's args are same as ours ... */
 	/* ... except handle is replaced by the object */
 	*MARK-- = SvTIED_obj((SV*)gv, mg);
@@ -553,7 +553,7 @@ PP(pp_close)
     else
 	gv = (GV*)POPs;
 
-    if ((mg = SvTIED_mg((SV*)gv, 'q'))) {
+    if ((mg = SvTIED_mg((SV*)gv, PERL_MAGIC_tiedscalar))) {
 	PUSHMARK(SP);
 	XPUSHs(SvTIED_obj((SV*)gv, mg));
 	PUTBACK;
@@ -635,7 +635,7 @@ PP(pp_fileno)
 	RETPUSHUNDEF;
     gv = (GV*)POPs;
 
-    if (gv && (mg = SvTIED_mg((SV*)gv, 'q'))) {
+    if (gv && (mg = SvTIED_mg((SV*)gv, PERL_MAGIC_tiedscalar))) {
 	PUSHMARK(SP);
 	XPUSHs(SvTIED_obj((SV*)gv, mg));
 	PUTBACK;
@@ -703,7 +703,7 @@ PP(pp_binmode)
 
     gv = (GV*)POPs;
 
-    if (gv && (mg = SvTIED_mg((SV*)gv, 'q'))) {
+    if (gv && (mg = SvTIED_mg((SV*)gv, PERL_MAGIC_tiedscalar))) {
 	PUSHMARK(SP);
 	XPUSHs(SvTIED_obj((SV*)gv, mg));
 	if (discp)
@@ -744,7 +744,7 @@ PP(pp_tie)
     SV *sv;
     I32 markoff = MARK - PL_stack_base;
     char *methname;
-    int how = 'P';
+    int how = PERL_MAGIC_tied;
     U32 items;
     STRLEN n_a;
 
@@ -763,11 +763,11 @@ PP(pp_tie)
 	    }
 #endif
 	    methname = "TIEHANDLE";
-	    how = 'q';
+	    how = PERL_MAGIC_tiedscalar;
 	    break;
 	default:
 	    methname = "TIESCALAR";
-	    how = 'q';
+	    how = PERL_MAGIC_tiedscalar;
 	    break;
     }
     items = SP - MARK++;
@@ -823,7 +823,8 @@ PP(pp_untie)
 {
     dSP;
     SV *sv = POPs;
-    char how = (SvTYPE(sv) == SVt_PVHV || SvTYPE(sv) == SVt_PVAV) ? 'P' : 'q';
+    char how = (SvTYPE(sv) == SVt_PVHV || SvTYPE(sv) == SVt_PVAV)
+		? PERL_MAGIC_tied : PERL_MAGIC_tiedscalar;
 
         MAGIC * mg ;
         if ((mg = SvTIED_mg(sv, how))) {
@@ -856,7 +857,8 @@ PP(pp_tied)
 {
     dSP;
     SV *sv = POPs;
-    char how = (SvTYPE(sv) == SVt_PVHV || SvTYPE(sv) == SVt_PVAV) ? 'P' : 'q';
+    char how = (SvTYPE(sv) == SVt_PVHV || SvTYPE(sv) == SVt_PVAV)
+		? PERL_MAGIC_tied : PERL_MAGIC_tiedscalar;
     MAGIC *mg;
 
     if ((mg = SvTIED_mg(sv, how))) {
@@ -919,8 +921,8 @@ PP(pp_dbmopen)
     }
 
     if (sv_isobject(TOPs)) {
-	sv_unmagic((SV *) hv, 'P');
-	sv_magic((SV*)hv, TOPs, 'P', Nullch, 0);
+	sv_unmagic((SV *) hv, PERL_MAGIC_tied);
+	sv_magic((SV*)hv, TOPs, PERL_MAGIC_tied, Nullch, 0);
     }
     LEAVE;
     RETURN;
@@ -1127,7 +1129,7 @@ PP(pp_getc)
     else
 	gv = (GV*)POPs;
 
-    if ((mg = SvTIED_mg((SV*)gv, 'q'))) {
+    if ((mg = SvTIED_mg((SV*)gv, PERL_MAGIC_tiedscalar))) {
 	I32 gimme = GIMME_V;
 	PUSHMARK(SP);
 	XPUSHs(SvTIED_obj((SV*)gv, mg));
@@ -1384,7 +1386,7 @@ PP(pp_prtf)
     else
 	gv = PL_defoutgv;
 
-    if ((mg = SvTIED_mg((SV*)gv, 'q'))) {
+    if ((mg = SvTIED_mg((SV*)gv, PERL_MAGIC_tiedscalar))) {
 	if (MARK == ORIGMARK) {
 	    MEXTEND(SP, 1);
 	    ++MARK;
@@ -1503,7 +1505,7 @@ PP(pp_sysread)
 
     gv = (GV*)*++MARK;
     if ((PL_op->op_type == OP_READ || PL_op->op_type == OP_SYSREAD) &&
-	(mg = SvTIED_mg((SV*)gv, 'q')))
+	(mg = SvTIED_mg((SV*)gv, PERL_MAGIC_tiedscalar)))
     {
 	SV *sv;
 	
@@ -1729,7 +1731,9 @@ PP(pp_send)
     MAGIC *mg;
 
     gv = (GV*)*++MARK;
-    if (PL_op->op_type == OP_SYSWRITE && (mg = SvTIED_mg((SV*)gv, 'q'))) {
+    if (PL_op->op_type == OP_SYSWRITE
+		&& (mg = SvTIED_mg((SV*)gv, PERL_MAGIC_tiedscalar)))
+    {
 	SV *sv;
 	
 	PUSHMARK(MARK-1);
@@ -1874,7 +1878,7 @@ PP(pp_eof)
     else
 	gv = PL_last_in_gv = (GV*)POPs;		/* eof(FH) */
 
-    if (gv && (mg = SvTIED_mg((SV*)gv, 'q'))) {
+    if (gv && (mg = SvTIED_mg((SV*)gv, PERL_MAGIC_tiedscalar))) {
 	PUSHMARK(SP);
 	XPUSHs(SvTIED_obj((SV*)gv, mg));
 	PUTBACK;
@@ -1900,7 +1904,7 @@ PP(pp_tell)
     else
 	gv = PL_last_in_gv = (GV*)POPs;
 
-    if (gv && (mg = SvTIED_mg((SV*)gv, 'q'))) {
+    if (gv && (mg = SvTIED_mg((SV*)gv, PERL_MAGIC_tiedscalar))) {
 	PUSHMARK(SP);
 	XPUSHs(SvTIED_obj((SV*)gv, mg));
 	PUTBACK;
@@ -1938,7 +1942,7 @@ PP(pp_sysseek)
 
     gv = PL_last_in_gv = (GV*)POPs;
 
-    if (gv && (mg = SvTIED_mg((SV*)gv, 'q'))) {
+    if (gv && (mg = SvTIED_mg((SV*)gv, PERL_MAGIC_tiedscalar))) {
 	PUSHMARK(SP);
 	XPUSHs(SvTIED_obj((SV*)gv, mg));
 #if LSEEKSIZE > IVSIZE
diff --git a/regexec.c b/regexec.c
index d60e7c75c8..9ba61d74be 100644
--- a/regexec.c
+++ b/regexec.c
@@ -1474,7 +1474,8 @@ Perl_regexec_flags(pTHX_ register regexp *prog, char *stringarg, register char *
 	    PL_reg_ganch = startpos;
 	else if (sv && SvTYPE(sv) >= SVt_PVMG
 		  && SvMAGIC(sv)
-		  && (mg = mg_find(sv, 'g')) && mg->mg_len >= 0) {
+		  && (mg = mg_find(sv, PERL_MAGIC_regex_global))
+		  && mg->mg_len >= 0) {
 	    PL_reg_ganch = strbeg + mg->mg_len;	/* Defined pos() */
 	    if (prog->reganch & ROPT_ANCH_GPOS) {
 		if (s > PL_reg_ganch)
@@ -1825,10 +1826,11 @@ S_regtry(pTHX_ regexp *prog, char *startpos)
 	    }
 	
 	    if (!(SvTYPE(PL_reg_sv) >= SVt_PVMG && SvMAGIC(PL_reg_sv)
-		  && (mg = mg_find(PL_reg_sv, 'g')))) {
+		  && (mg = mg_find(PL_reg_sv, PERL_MAGIC_regex_global)))) {
 		/* prepare for quick setting of pos */
-		sv_magic(PL_reg_sv, (SV*)0, 'g', Nullch, 0);
-		mg = mg_find(PL_reg_sv, 'g');
+		sv_magic(PL_reg_sv, (SV*)0,
+			PERL_MAGIC_regex_global, Nullch, 0);
+		mg = mg_find(PL_reg_sv, PERL_MAGIC_regex_global);
 		mg->mg_len = -1;
 	    }
 	    PL_reg_magic    = mg;
@@ -2502,7 +2504,7 @@ S_regmatch(pTHX_ regnode *prog)
 			SV *sv = SvROK(ret) ? SvRV(ret) : ret;
 
 			if(SvMAGICAL(sv))
-			    mg = mg_find(sv, 'r');
+			    mg = mg_find(sv, PERL_MAGIC_qr);
 		    }
 		    if (mg) {
 			re = (regexp *)mg->mg_obj;
@@ -2520,7 +2522,8 @@ S_regmatch(pTHX_ regnode *prog)
 			re = CALLREGCOMP(aTHX_ t, t + len, &pm);
 			if (!(SvFLAGS(ret)
 			      & (SVs_TEMP | SVs_PADTMP | SVf_READONLY)))
-			    sv_magic(ret,(SV*)ReREFCNT_inc(re),'r',0,0);
+			    sv_magic(ret,(SV*)ReREFCNT_inc(re),
+					PERL_MAGIC_qr,0,0);
 			PL_regprecomp = oprecomp;
 			PL_regsize = osize;
 			PL_regnpar = onpar;
diff --git a/scope.c b/scope.c
index 31c6f01d56..d9e1ecf167 100644
--- a/scope.c
+++ b/scope.c
@@ -197,7 +197,8 @@ S_save_scalar_at(pTHX_ SV **sptr)
 	    MAGIC* mg;
 	    bool oldtainted = PL_tainted;
 	    mg_get(osv);		/* note, can croak! */
-	    if (PL_tainting && PL_tainted && (mg = mg_find(osv, 't'))) {
+	    if (PL_tainting && PL_tainted &&
+			(mg = mg_find(osv, PERL_MAGIC_taint))) {
 		SAVESPTR(mg->mg_obj);
 		mg->mg_obj = osv;
 	    }
@@ -901,7 +902,7 @@ Perl_leave_scope(pTHX_ I32 base)
 	    if (ptr) {
 		sv = *(SV**)ptr;
 		if (sv && sv != &PL_sv_undef) {
-		    if (SvTIED_mg((SV*)av, 'P'))
+		    if (SvTIED_mg((SV*)av, PERL_MAGIC_tied))
 			(void)SvREFCNT_inc(sv);
 		    SvREFCNT_dec(av);
 		    goto restore_sv;
@@ -919,7 +920,7 @@ Perl_leave_scope(pTHX_ I32 base)
 		SV *oval = HeVAL((HE*)ptr);
 		if (oval && oval != &PL_sv_undef) {
 		    ptr = &HeVAL((HE*)ptr);
-		    if (SvTIED_mg((SV*)hv, 'P'))
+		    if (SvTIED_mg((SV*)hv, PERL_MAGIC_tied))
 			(void)SvREFCNT_inc(*(SV**)ptr);
 		    SvREFCNT_dec(hv);
 		    SvREFCNT_dec(sv);
diff --git a/sv.c b/sv.c
index 65a3279d6b..a448938d46 100644
--- a/sv.c
+++ b/sv.c
@@ -2699,7 +2699,7 @@ Perl_sv_2pv(pTHX_ register SV *sv, STRLEN *lp)
 			   (SVs_OBJECT|SVf_OK|SVs_GMG|SVs_SMG|SVs_RMG))
 			  == (SVs_OBJECT|SVs_RMG))
 			 && strEQ(s=HvNAME(SvSTASH(sv)), "Regexp")
-			 && (mg = mg_find(sv, 'r'))) {
+			 && (mg = mg_find(sv, PERL_MAGIC_qr))) {
 			regexp *re = (regexp *)mg->mg_obj;
 
 			if (!mg->mg_ptr) {
@@ -3270,7 +3270,7 @@ Perl_sv_setsv(pTHX_ SV *dstr, register SV *sstr)
 		char *name = GvNAME(sstr);
 		STRLEN len = GvNAMELEN(sstr);
 		sv_upgrade(dstr, SVt_PVGV);
-		sv_magic(dstr, dstr, '*', Nullch, 0);
+		sv_magic(dstr, dstr, PERL_MAGIC_glob, Nullch, 0);
 		GvSTASH(dstr) = (HV*)SvREFCNT_inc(GvSTASH(sstr));
 		GvNAME(dstr) = savepvn(name, len);
 		GvNAMELEN(dstr) = len;
@@ -3995,12 +3995,23 @@ Perl_sv_magic(pTHX_ register SV *sv, SV *obj, int how, const char *name, I32 nam
     MAGIC* mg;
 
     if (SvREADONLY(sv)) {
-	if (PL_curcop != &PL_compiling && !strchr("gBf", how))
+	if (PL_curcop != &PL_compiling
+	    /* XXX this used to be !strchr("gBf", how), which seems to
+	     * implicity be equal to !strchr("gBf\0", how), ie \0 matches
+	     * too. I find this suprising, but have hadded PERL_MAGIC_sv
+	     * to the list of things to check - DAPM 19-May-01 */
+	    && how != PERL_MAGIC_regex_global
+	    && how != PERL_MAGIC_bm
+	    && how != PERL_MAGIC_fm
+	    && how != PERL_MAGIC_sv 
+	   )
+	{
 	    Perl_croak(aTHX_ PL_no_modify);
+	}
     }
-    if (SvMAGICAL(sv) || (how == 't' && SvTYPE(sv) >= SVt_PVMG)) {
+    if (SvMAGICAL(sv) || (how == PERL_MAGIC_taint && SvTYPE(sv) >= SVt_PVMG)) {
 	if (SvMAGIC(sv) && (mg = mg_find(sv, how))) {
-	    if (how == 't')
+	    if (how == PERL_MAGIC_taint)
 		mg->mg_len |= 1;
 	    return;
 	}
@@ -4016,7 +4027,9 @@ Perl_sv_magic(pTHX_ register SV *sv, SV *obj, int how, const char *name, I32 nam
        each other.  To prevent a avoid a reference loop that would prevent such
        objects being freed, we look for such loops and if we find one we avoid
        incrementing the object refcount. */
-    if (!obj || obj == sv || how == '#' || how == 'r' ||
+    if (!obj || obj == sv ||
+	how == PERL_MAGIC_arylen ||
+	how == PERL_MAGIC_qr ||
 	(SvTYPE(obj) == SVt_PVGV &&
 	    (GvSV(obj) == sv || GvHV(obj) == (HV*)sv || GvAV(obj) == (AV*)sv ||
 	    GvCV(obj) == (CV*)sv || GvIOp(obj) == (IO*)sv ||
@@ -4038,117 +4051,118 @@ Perl_sv_magic(pTHX_ register SV *sv, SV *obj, int how, const char *name, I32 nam
     }
 
     switch (how) {
-    case 0:
+    case PERL_MAGIC_sv:
 	mg->mg_virtual = &PL_vtbl_sv;
 	break;
-    case 'A':
+    case PERL_MAGIC_overload:
         mg->mg_virtual = &PL_vtbl_amagic;
         break;
-    case 'a':
+    case PERL_MAGIC_overload_elem:
         mg->mg_virtual = &PL_vtbl_amagicelem;
         break;
-    case 'c':
+    case PERL_MAGIC_overload_table:
         mg->mg_virtual = &PL_vtbl_ovrld;
         break;
-    case 'B':
+    case PERL_MAGIC_bm:
 	mg->mg_virtual = &PL_vtbl_bm;
 	break;
-    case 'D':
+    case PERL_MAGIC_regdata:
 	mg->mg_virtual = &PL_vtbl_regdata;
 	break;
-    case 'd':
+    case PERL_MAGIC_regdatum:
 	mg->mg_virtual = &PL_vtbl_regdatum;
 	break;
-    case 'E':
+    case PERL_MAGIC_env:
 	mg->mg_virtual = &PL_vtbl_env;
 	break;
-    case 'f':
+    case PERL_MAGIC_fm:
 	mg->mg_virtual = &PL_vtbl_fm;
 	break;
-    case 'e':
+    case PERL_MAGIC_envelem:
 	mg->mg_virtual = &PL_vtbl_envelem;
 	break;
-    case 'g':
+    case PERL_MAGIC_regex_global:
 	mg->mg_virtual = &PL_vtbl_mglob;
 	break;
-    case 'I':
+    case PERL_MAGIC_isa:
 	mg->mg_virtual = &PL_vtbl_isa;
 	break;
-    case 'i':
+    case PERL_MAGIC_isaelem:
 	mg->mg_virtual = &PL_vtbl_isaelem;
 	break;
-    case 'k':
+    case PERL_MAGIC_nkeys:
 	mg->mg_virtual = &PL_vtbl_nkeys;
 	break;
-    case 'L':
+    case PERL_MAGIC_dbfile:
 	SvRMAGICAL_on(sv);
 	mg->mg_virtual = 0;
 	break;
-    case 'l':
+    case PERL_MAGIC_dbline:
 	mg->mg_virtual = &PL_vtbl_dbline;
 	break;
 #ifdef USE_THREADS
-    case 'm':
+    case PERL_MAGIC_mutex:
 	mg->mg_virtual = &PL_vtbl_mutex;
 	break;
 #endif /* USE_THREADS */
 #ifdef USE_LOCALE_COLLATE
-    case 'o':
+    case PERL_MAGIC_collxfrm:
         mg->mg_virtual = &PL_vtbl_collxfrm;
         break;
 #endif /* USE_LOCALE_COLLATE */
-    case 'P':
+    case PERL_MAGIC_tied:
 	mg->mg_virtual = &PL_vtbl_pack;
 	break;
-    case 'p':
-    case 'q':
+    case PERL_MAGIC_tiedelem:
+    case PERL_MAGIC_tiedscalar:
 	mg->mg_virtual = &PL_vtbl_packelem;
 	break;
-    case 'r':
+    case PERL_MAGIC_qr:
 	mg->mg_virtual = &PL_vtbl_regexp;
 	break;
-    case 'S':
+    case PERL_MAGIC_sig:
 	mg->mg_virtual = &PL_vtbl_sig;
 	break;
-    case 's':
+    case PERL_MAGIC_sigelem:
 	mg->mg_virtual = &PL_vtbl_sigelem;
 	break;
-    case 't':
+    case PERL_MAGIC_taint:
 	mg->mg_virtual = &PL_vtbl_taint;
 	mg->mg_len = 1;
 	break;
-    case 'U':
+    case PERL_MAGIC_uvar:
 	mg->mg_virtual = &PL_vtbl_uvar;
 	break;
-    case 'v':
+    case PERL_MAGIC_vec:
 	mg->mg_virtual = &PL_vtbl_vec;
 	break;
-    case 'x':
+    case PERL_MAGIC_substr:
 	mg->mg_virtual = &PL_vtbl_substr;
 	break;
-    case 'y':
+    case PERL_MAGIC_defelem:
 	mg->mg_virtual = &PL_vtbl_defelem;
 	break;
-    case '*':
+    case PERL_MAGIC_glob:
 	mg->mg_virtual = &PL_vtbl_glob;
 	break;
-    case '#':
+    case PERL_MAGIC_arylen:
 	mg->mg_virtual = &PL_vtbl_arylen;
 	break;
-    case '.':
+    case PERL_MAGIC_pos:
 	mg->mg_virtual = &PL_vtbl_pos;
 	break;
-    case '<':
+    case PERL_MAGIC_backref:
 	mg->mg_virtual = &PL_vtbl_backref;
 	break;
-    case '~':	/* Reserved for use by extensions not perl internals.	*/
+    case PERL_MAGIC_ext:
+	/* Reserved for use by extensions not perl internals.	        */
 	/* Useful for attaching extension internal data to perl vars.	*/
 	/* Note that multiple extensions may clash if magical scalars	*/
 	/* etc holding private data from one are passed to another.	*/
 	SvRMAGICAL_on(sv);
 	break;
     default:
-	Perl_croak(aTHX_ "Don't know how to handle magic of type '%c'", how);
+	Perl_croak(aTHX_ "Don't know how to handle magic of type \\%o", how);
     }
     mg_magical(sv);
     if (SvGMAGICAL(sv))
@@ -4177,7 +4191,7 @@ Perl_sv_unmagic(pTHX_ SV *sv, int type)
 	    *mgp = mg->mg_moremagic;
 	    if (vtbl && vtbl->svt_free)
 		CALL_FPTR(vtbl->svt_free)(aTHX_ sv, mg);
-	    if (mg->mg_ptr && mg->mg_type != 'g') {
+	    if (mg->mg_ptr && mg->mg_type != PERL_MAGIC_regex_global) {
 		if (mg->mg_len >= 0)
 		    Safefree(mg->mg_ptr);
 		else if (mg->mg_len == HEf_SVKEY)
@@ -4231,11 +4245,11 @@ S_sv_add_backref(pTHX_ SV *tsv, SV *sv)
 {
     AV *av;
     MAGIC *mg;
-    if (SvMAGICAL(tsv) && (mg = mg_find(tsv, '<')))
+    if (SvMAGICAL(tsv) && (mg = mg_find(tsv, PERL_MAGIC_backref)))
 	av = (AV*)mg->mg_obj;
     else {
 	av = newAV();
-	sv_magic(tsv, (SV*)av, '<', NULL, 0);
+	sv_magic(tsv, (SV*)av, PERL_MAGIC_backref, NULL, 0);
 	SvREFCNT_dec(av);           /* for sv_magic */
     }
     av_push(av,sv);
@@ -4249,7 +4263,7 @@ S_sv_del_backref(pTHX_ SV *sv)
     I32 i;
     SV *tsv = SvRV(sv);
     MAGIC *mg;
-    if (!SvMAGICAL(tsv) || !(mg = mg_find(tsv, '<')))
+    if (!SvMAGICAL(tsv) || !(mg = mg_find(tsv, PERL_MAGIC_backref)))
 	Perl_croak(aTHX_ "panic: del_backref");
     av = (AV *)mg->mg_obj;
     svp = AvARRAY(av);
@@ -4954,7 +4968,7 @@ Perl_sv_cmp_locale(pTHX_ register SV *sv1, register SV *sv2)
 
 #ifdef USE_LOCALE_COLLATE
 /*
- * Any scalar variable may carry an 'o' magic that contains the
+ * Any scalar variable may carry PERL_MAGIC_collxfrm magic that contains the
  * scalar data of the variable transformed to such a format that
  * a normal memory comparison can be used to compare the data
  * according to the locale settings.
@@ -4964,7 +4978,7 @@ Perl_sv_collxfrm(pTHX_ SV *sv, STRLEN *nxp)
 {
     MAGIC *mg;
 
-    mg = SvMAGICAL(sv) ? mg_find(sv, 'o') : (MAGIC *) NULL;
+    mg = SvMAGICAL(sv) ? mg_find(sv, PERL_MAGIC_collxfrm) : (MAGIC *) NULL;
     if (!mg || !mg->mg_ptr || *(U32*)mg->mg_ptr != PL_collation_ix) {
 	char *s, *xf;
 	STRLEN len, xlen;
@@ -4979,8 +4993,8 @@ Perl_sv_collxfrm(pTHX_ SV *sv, STRLEN *nxp)
 		return xf + sizeof(PL_collation_ix);
 	    }
 	    if (! mg) {
-		sv_magic(sv, 0, 'o', 0, 0);
-		mg = mg_find(sv, 'o');
+		sv_magic(sv, 0, PERL_MAGIC_collxfrm, 0, 0);
+		mg = mg_find(sv, PERL_MAGIC_collxfrm);
 		assert(mg);
 	    }
 	    mg->mg_ptr = xf;
@@ -6544,7 +6558,7 @@ S_sv_unglob(pTHX_ SV *sv)
 	SvREFCNT_dec(GvSTASH(sv));
 	GvSTASH(sv) = Nullhv;
     }
-    sv_unmagic(sv, '*');
+    sv_unmagic(sv, PERL_MAGIC_glob);
     Safefree(GvNAME(sv));
     GvMULTI_off(sv);
 
@@ -6611,14 +6625,14 @@ Perl_sv_unref(pTHX_ SV *sv)
 void
 Perl_sv_taint(pTHX_ SV *sv)
 {
-    sv_magic((sv), Nullsv, 't', Nullch, 0);
+    sv_magic((sv), Nullsv, PERL_MAGIC_taint, Nullch, 0);
 }
 
 void
 Perl_sv_untaint(pTHX_ SV *sv)
 {
     if (SvTYPE(sv) >= SVt_PVMG && SvMAGIC(sv)) {
-	MAGIC *mg = mg_find(sv, 't');
+	MAGIC *mg = mg_find(sv, PERL_MAGIC_taint);
 	if (mg)
 	    mg->mg_len &= ~1;
     }
@@ -6628,7 +6642,7 @@ bool
 Perl_sv_tainted(pTHX_ SV *sv)
 {
     if (SvTYPE(sv) >= SVt_PVMG && SvMAGIC(sv)) {
-	MAGIC *mg = mg_find(sv, 't');
+	MAGIC *mg = mg_find(sv, PERL_MAGIC_taint);
 	if (mg && ((mg->mg_len & 1) || ((mg->mg_len & 2) && mg->mg_obj == sv)))
 	    return TRUE;
     }
@@ -7705,7 +7719,7 @@ Perl_mg_dup(pTHX_ MAGIC *mg)
 	nmg->mg_private	= mg->mg_private;
 	nmg->mg_type	= mg->mg_type;
 	nmg->mg_flags	= mg->mg_flags;
-	if (mg->mg_type == 'r') {
+	if (mg->mg_type == PERL_MAGIC_qr) {
 	    nmg->mg_obj	= (SV*)re_dup((REGEXP*)mg->mg_obj);
 	}
 	else {
@@ -7715,10 +7729,12 @@ Perl_mg_dup(pTHX_ MAGIC *mg)
 	}
 	nmg->mg_len	= mg->mg_len;
 	nmg->mg_ptr	= mg->mg_ptr;	/* XXX random ptr? */
-	if (mg->mg_ptr && mg->mg_type != 'g') {
+	if (mg->mg_ptr && mg->mg_type != PERL_MAGIC_regex_global) {
 	    if (mg->mg_len >= 0) {
 		nmg->mg_ptr	= SAVEPVN(mg->mg_ptr, mg->mg_len);
-		if (mg->mg_type == 'c' && AMT_AMAGIC((AMT*)mg->mg_ptr)) {
+		if (mg->mg_type == PERL_MAGIC_overload_table &&
+			AMT_AMAGIC((AMT*)mg->mg_ptr))
+		{
 		    AMT *amtp = (AMT*)mg->mg_ptr;
 		    AMT *namtp = (AMT*)nmg->mg_ptr;
 		    I32 i;
diff --git a/t/lib/peek.t b/t/lib/peek.t
index 96e24a2e4f..c14dc9bdad 100644
--- a/t/lib/peek.t
+++ b/t/lib/peek.t
@@ -251,7 +251,7 @@ do_test(15,
     PV = 0
     MAGIC = $ADDR
       MG_VIRTUAL = $ADDR
-      MG_TYPE = \'r\'
+      MG_TYPE = PERL_MAGIC_qr\(r\)
       MG_OBJ = $ADDR
     STASH = $ADDR\\t"Regexp"');
 
@@ -283,7 +283,7 @@ do_test(17,
   NV = 0
   MAGIC = $ADDR
     MG_VIRTUAL = &PL_vtbl_glob
-    MG_TYPE = \'\\*\'
+    MG_TYPE = PERL_MAGIC_glob\(\*\)
     MG_OBJ = $ADDR
   NAME = "a"
   NAMELEN = 1
diff --git a/taint.c b/taint.c
index 7a8baac7b0..ab0b697ebb 100644
--- a/taint.c
+++ b/taint.c
@@ -66,7 +66,7 @@ Perl_taint_env(pTHX)
 	    TAINT;
 	    taint_proper("Insecure %s%s", "$ENV{DCL$PATH}");
 	}
-	if ((mg = mg_find(*svp, 'e')) && MgTAINTEDDIR(mg)) {
+	if ((mg = mg_find(*svp, PERL_MAGIC_envelem)) && MgTAINTEDDIR(mg)) {
 	    TAINT;
 	    taint_proper("Insecure directory in %s%s", "$ENV{DCL$PATH}");
 	}
@@ -81,7 +81,7 @@ Perl_taint_env(pTHX)
 	    TAINT;
 	    taint_proper("Insecure %s%s", "$ENV{PATH}");
 	}
-	if ((mg = mg_find(*svp, 'e')) && MgTAINTEDDIR(mg)) {
+	if ((mg = mg_find(*svp, PERL_MAGIC_envelem)) && MgTAINTEDDIR(mg)) {
 	    TAINT;
 	    taint_proper("Insecure directory in %s%s", "$ENV{PATH}");
 	}
diff --git a/util.c b/util.c
index 12c5f0ddc0..f91c86a341 100644
--- a/util.c
+++ b/util.c
@@ -1033,7 +1033,7 @@ Perl_fbm_compile(pTHX_ SV *sv, U32 flags)
 	    s--, i++;
 	}
     }
-    sv_magic(sv, Nullsv, 'B', Nullch, 0);	/* deep magic */
+    sv_magic(sv, Nullsv, PERL_MAGIC_bm, Nullch, 0);	/* deep magic */
     SvVALID_on(sv);
 
     s = (unsigned char*)(SvPVX(sv));		/* deeper magic */
@@ -3597,7 +3597,7 @@ Perl_condpair_magic(pTHX_ SV *sv)
     MAGIC *mg;
 
     SvUPGRADE(sv, SVt_PVMG);
-    mg = mg_find(sv, 'm');
+    mg = mg_find(sv, PERL_MAGIC_mutex);
     if (!mg) {
 	condpair_t *cp;
 
@@ -3607,7 +3607,7 @@ Perl_condpair_magic(pTHX_ SV *sv)
 	COND_INIT(&cp->cond);
 	cp->owner = 0;
 	LOCK_CRED_MUTEX;		/* XXX need separate mutex? */
-	mg = mg_find(sv, 'm');
+	mg = mg_find(sv, PERL_MAGIC_mutex);
 	if (mg) {
 	    /* someone else beat us to initialising it */
 	    UNLOCK_CRED_MUTEX;		/* XXX need separate mutex? */
@@ -3617,7 +3617,7 @@ Perl_condpair_magic(pTHX_ SV *sv)
 	    Safefree(cp);
 	}
 	else {
-	    sv_magic(sv, Nullsv, 'm', 0, 0);
+	    sv_magic(sv, Nullsv, PERL_MAGIC_mutex, 0, 0);
 	    mg = SvMAGIC(sv);
 	    mg->mg_ptr = (char *)cp;
 	    mg->mg_len = sizeof(cp);
@@ -3761,7 +3761,7 @@ Perl_new_struct_thread(pTHX_ struct perl_thread *t)
 	if (*svp && *svp != &PL_sv_undef) {
 	    SV *sv = newSVsv(*svp);
 	    av_store(thr->threadsv, i, sv);
-	    sv_magic(sv, 0, 0, &PL_threadsv_names[i], 1);
+	    sv_magic(sv, 0, PERL_MAGIC_sv, &PL_threadsv_names[i], 1);
 	    DEBUG_S(PerlIO_printf(Perl_debug_log,
 		"new_struct_thread: copied threadsv %"IVdf" %p->%p\n",
 				  (IV)i, t, thr));
diff --git a/xsutils.c b/xsutils.c
index 187d9f75c1..3493565bc7 100644
--- a/xsutils.c
+++ b/xsutils.c
@@ -235,7 +235,7 @@ usage:
 		stash = CvSTASH(sv);
 	    break;
 	case SVt_PVMG:
-	    if (!(SvFAKE(sv) && SvTIED_mg(sv, '*')))
+	    if (!(SvFAKE(sv) && SvTIED_mg(sv, PERL_MAGIC_glob)))
 		break;
 	    /*FALLTHROUGH*/
 	case SVt_PVGV: