eval $undef should emit one warning, not three.

Also ensure that eval $undef clears $@ (it did, but only by luck)

p4raw-id: //depot/perl@29193

3 files changed, 4 insertions, 12 deletions

diff --git a/pp_ctl.c b/pp_ctl.c
index 708f2fa07a..7b91e86c23 100644
--- a/pp_ctl.c
+++ b/pp_ctl.c
@@ -3455,8 +3455,6 @@ PP(pp_entereval)
     }
     sv = POPs;
 
-    if (!SvPV_nolen_const(sv))
-	RETPUSHUNDEF;
     TAINT_PROPER("eval");
 
     ENTER;
diff --git a/t/lib/warnings/9uninit b/t/lib/warnings/9uninit
index 9b60808d0d..f49ca66474 100644
--- a/t/lib/warnings/9uninit
+++ b/t/lib/warnings/9uninit
@@ -1289,11 +1289,7 @@ $v = eval;
 $v = eval $m1;
 EXPECT
 Use of uninitialized value $_ in eval "string" at - line 4.
-Use of uninitialized value $_ in eval "string" at - line 4.
-Use of uninitialized value UTF8?'':'$_ 'in eval "string" at - line 4.
-Use of uninitialized value $m1 in eval "string" at - line 5.
 Use of uninitialized value $m1 in eval "string" at - line 5.
-Use of uninitialized value UTF8?'':'$m1 'in eval "string" at - line 5.
 ########
 use warnings 'uninitialized';
 my ($m1);
diff --git a/toke.c b/toke.c
index 4513c4055f..9b48f96983 100644
--- a/toke.c
+++ b/toke.c
@@ -662,13 +662,11 @@ Perl_lex_start(pTHX_ SV *line)
     PL_lex_inwhat = 0;
     PL_sublex_info.sub_inwhat = 0;
     PL_linestr = line;
-    if (SvREADONLY(PL_linestr))
-	PL_linestr = sv_2mortal(newSVsv(PL_linestr));
     s = SvPV_const(PL_linestr, len);
-    if (!len || s[len-1] != ';') {
-	if (!(SvFLAGS(PL_linestr) & SVs_TEMP))
-	    PL_linestr = sv_2mortal(newSVsv(PL_linestr));
-	sv_catpvs(PL_linestr, "\n;");
+    if (SvREADONLY(PL_linestr) || !len || s[len-1] != ';') {
+	PL_linestr = sv_2mortal(len ? newSVsv(PL_linestr) : newSVpvn(s, 0));
+	if (!len || s[len-1] != ';')
+	    sv_catpvs(PL_linestr, "\n;");
     }
     SvTEMP_off(PL_linestr);
     PL_oldoldbufptr = PL_oldbufptr = PL_bufptr = PL_linestart = SvPVX(PL_linestr);