Merge branch 'const_posix_invlists' into blead

What characters certain POSIX classes match, like [[:xdigit:]] are
compiled into a C header file, thus avoiding the necessity of reading
them in from disk at run-time.  This merge makes those fully const, so
that they can get loaded as part of a read-only text segment.  The sv's
that contain these are set so that SvLEN is 0; this means (from my
looking at the code without any experience in this area) that copies are
not made when they are dup'd, such as when threads are created.

A new svtype is created for inversion lists, using the single
available slot, renumbering them.

The first few commits instead use an existing svtype, repurposing
some of its fields for use by inversion lists.  This was done so that
this could be done in a maintenance release, if necessary.  (Their not
being fully const can interfere with -DPERL_GLOBAL_STRUCT_PRIVATE.)
And also, should it become necessary to create an svtype for some other
purpose, we can revert to that point in the branch.

14 files changed, 381 insertions, 466 deletions

diff --git a/charclass_invlists.h b/charclass_invlists.h
index b5d71afb16..19500e7a12 100644
--- a/charclass_invlists.h
+++ b/charclass_invlists.h
@@ -9,28 +9,25 @@
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV Latin1_invlist[] = {
+static const UV Latin1_invlist[] = {
 	2,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	0,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
-	256,
-	0
+	1826693541, /* Version and data structure type */
+	0,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
+	256
 };
 
 #endif
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV AboveLatin1_invlist[] = {
+static const UV AboveLatin1_invlist[] = {
 	1,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	256
 };
 
@@ -38,28 +35,25 @@ static UV AboveLatin1_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV ASCII_invlist[] = {
+static const UV ASCII_invlist[] = {
 	2,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	0,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
-	128,
-	0
+	1826693541, /* Version and data structure type */
+	0,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
+	128
 };
 
 #endif
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV L1Cased_invlist[] = {
+static const UV L1Cased_invlist[] = {
 	16,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	65,
 	91,
 	97,
@@ -82,13 +76,12 @@ static UV L1Cased_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV VertSpace_invlist[] = {
+static const UV VertSpace_invlist[] = {
 	6,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	10,
 	14,
 	133,
@@ -101,13 +94,12 @@ static UV VertSpace_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV PerlSpace_invlist[] = {
+static const UV PerlSpace_invlist[] = {
 	4,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	9,
 	14,
 	32,
@@ -118,13 +110,12 @@ static UV PerlSpace_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV XPerlSpace_invlist[] = {
+static const UV XPerlSpace_invlist[] = {
 	22,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	9,
 	14,
 	32,
@@ -153,13 +144,12 @@ static UV XPerlSpace_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV PosixAlnum_invlist[] = {
+static const UV PosixAlnum_invlist[] = {
 	6,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	48,
 	58,
 	65,
@@ -172,13 +162,12 @@ static UV PosixAlnum_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV L1PosixAlnum_invlist[] = {
+static const UV L1PosixAlnum_invlist[] = {
 	18,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	48,
 	58,
 	65,
@@ -203,13 +192,12 @@ static UV L1PosixAlnum_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV PosixAlpha_invlist[] = {
+static const UV PosixAlpha_invlist[] = {
 	4,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	65,
 	91,
 	97,
@@ -220,13 +208,12 @@ static UV PosixAlpha_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV L1PosixAlpha_invlist[] = {
+static const UV L1PosixAlpha_invlist[] = {
 	16,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	65,
 	91,
 	97,
@@ -249,13 +236,12 @@ static UV L1PosixAlpha_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV PosixBlank_invlist[] = {
+static const UV PosixBlank_invlist[] = {
 	4,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	9,
 	10,
 	32,
@@ -266,13 +252,12 @@ static UV PosixBlank_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV XPosixBlank_invlist[] = {
+static const UV XPosixBlank_invlist[] = {
 	18,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	9,
 	10,
 	32,
@@ -297,47 +282,42 @@ static UV XPosixBlank_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV PosixCntrl_invlist[] = {
+static const UV PosixCntrl_invlist[] = {
 	4,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	0,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	0,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	32,
 	127,
-	128,
-	0
+	128
 };
 
 #endif
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV XPosixCntrl_invlist[] = {
+static const UV XPosixCntrl_invlist[] = {
 	4,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	0,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	0,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	32,
 	127,
-	160,
-	0
+	160
 };
 
 #endif
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV PosixDigit_invlist[] = {
+static const UV PosixDigit_invlist[] = {
 	2,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	48,
 	58
 };
@@ -346,13 +326,12 @@ static UV PosixDigit_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV PosixGraph_invlist[] = {
+static const UV PosixGraph_invlist[] = {
 	2,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	33,
 	127
 };
@@ -361,13 +340,12 @@ static UV PosixGraph_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV L1PosixGraph_invlist[] = {
+static const UV L1PosixGraph_invlist[] = {
 	4,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	33,
 	127,
 	161,
@@ -378,13 +356,12 @@ static UV L1PosixGraph_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV PosixLower_invlist[] = {
+static const UV PosixLower_invlist[] = {
 	2,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	97,
 	123
 };
@@ -393,13 +370,12 @@ static UV PosixLower_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV L1PosixLower_invlist[] = {
+static const UV L1PosixLower_invlist[] = {
 	12,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	97,
 	123,
 	170,
@@ -418,13 +394,12 @@ static UV L1PosixLower_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV PosixPrint_invlist[] = {
+static const UV PosixPrint_invlist[] = {
 	2,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	32,
 	127
 };
@@ -433,13 +408,12 @@ static UV PosixPrint_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV L1PosixPrint_invlist[] = {
+static const UV L1PosixPrint_invlist[] = {
 	4,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	32,
 	127,
 	160,
@@ -450,13 +424,12 @@ static UV L1PosixPrint_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV PosixPunct_invlist[] = {
+static const UV PosixPunct_invlist[] = {
 	8,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	33,
 	48,
 	58,
@@ -471,13 +444,12 @@ static UV PosixPunct_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV L1PosixPunct_invlist[] = {
+static const UV L1PosixPunct_invlist[] = {
 	20,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	33,
 	48,
 	58,
@@ -504,13 +476,12 @@ static UV L1PosixPunct_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV PosixSpace_invlist[] = {
+static const UV PosixSpace_invlist[] = {
 	4,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	9,
 	14,
 	32,
@@ -521,13 +492,12 @@ static UV PosixSpace_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV XPosixSpace_invlist[] = {
+static const UV XPosixSpace_invlist[] = {
 	22,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	9,
 	14,
 	32,
@@ -556,13 +526,12 @@ static UV XPosixSpace_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV PosixUpper_invlist[] = {
+static const UV PosixUpper_invlist[] = {
 	2,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	65,
 	91
 };
@@ -571,13 +540,12 @@ static UV PosixUpper_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV L1PosixUpper_invlist[] = {
+static const UV L1PosixUpper_invlist[] = {
 	6,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	65,
 	91,
 	192,
@@ -590,13 +558,12 @@ static UV L1PosixUpper_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV PosixWord_invlist[] = {
+static const UV PosixWord_invlist[] = {
 	8,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	48,
 	58,
 	65,
@@ -611,13 +578,12 @@ static UV PosixWord_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV L1PosixWord_invlist[] = {
+static const UV L1PosixWord_invlist[] = {
 	20,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	48,
 	58,
 	65,
@@ -644,13 +610,12 @@ static UV L1PosixWord_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV PosixXDigit_invlist[] = {
+static const UV PosixXDigit_invlist[] = {
 	6,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	48,
 	58,
 	65,
@@ -663,13 +628,12 @@ static UV PosixXDigit_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV XPosixXDigit_invlist[] = {
+static const UV XPosixXDigit_invlist[] = {
 	12,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	48,
 	58,
 	65,
@@ -686,13 +650,12 @@ static UV XPosixXDigit_invlist[] = {
 
 #endif
 
-static UV NonL1_Perl_Non_Final_Folds_invlist[] = {
+static const UV NonL1_Perl_Non_Final_Folds_invlist[] = {
 	44,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	700,
 	701,
 	776,
@@ -741,13 +704,12 @@ static UV NonL1_Perl_Non_Final_Folds_invlist[] = {
 
 #ifndef PERL_IN_XSUB_RE
 
-static UV _Perl_Multi_Char_Folds_invlist[] = {
+static const UV _Perl_Multi_Char_Folds_invlist[] = {
 	58,	/* Number of elements */
-	0,	/* Current iteration position */
-	0,	/* Cache of previous search index result */
-	290655244, /* Version and data structure type */
-	1,	/* 0 if this is the first element of the list proper;
-		   1 if the next element is the first */
+	1826693541, /* Version and data structure type */
+	1,	/* 0 if the list starts at 0;
+		   1 if it starts at the element beyond 0 */
+	0,
 	223,
 	224,
 	304,
diff --git a/dist/Storable/Storable.pm b/dist/Storable/Storable.pm
index 1a73c3fafa..5f63871bb8 100644
--- a/dist/Storable/Storable.pm
+++ b/dist/Storable/Storable.pm
@@ -21,7 +21,7 @@ package Storable; @ISA = qw(Exporter);
 
 use vars qw($canonical $forgive_me $VERSION);
 
-$VERSION = '2.43';
+$VERSION = '2.44';
 
 BEGIN {
     if (eval { local $SIG{__DIE__}; require Log::Agent; 1 }) {
diff --git a/dist/Storable/Storable.xs b/dist/Storable/Storable.xs
index 08641cdd38..f21f053a9d 100644
--- a/dist/Storable/Storable.xs
+++ b/dist/Storable/Storable.xs
@@ -3469,7 +3469,7 @@ static int sv_type(pTHX_ SV *sv)
 	case SVt_PVCV:
 		return svis_CODE;
 #if PERL_VERSION > 8
-	/* case SVt_DUMMY: */
+	/* case SVt_INVLIST: */
 #endif
 	default:
 		break;
diff --git a/dump.c b/dump.c
index 5ca838b043..6ba4fd2425 100644
--- a/dump.c
+++ b/dump.c
@@ -27,13 +27,12 @@
 #include "perl.h"
 #include "regcomp.h"
 
-
 static const char* const svtypenames[SVt_LAST] = {
     "NULL",
-    "DUMMY",
     "IV",
     "NV",
     "PV",
+    "INVLIST",
     "PVIV",
     "PVNV",
     "PVMG",
@@ -50,10 +49,10 @@ static const char* const svtypenames[SVt_LAST] = {
 
 static const char* const svshorttypenames[SVt_LAST] = {
     "UNDEF",
-    "DUMMY",
     "IV",
     "NV",
     "PV",
+    "INVLST",
     "PVIV",
     "PVNV",
     "PVMG",
@@ -2798,7 +2797,7 @@ Perl_sv_xmlpeek(pTHX_ SV *sv)
     case SVt_PVGV:
 	sv_catpv(t, " GV=\"");
 	break;
-    case SVt_DUMMY:
+    case SVt_INVLIST:
 	sv_catpv(t, " DUMMY=\"");
 	break;
     case SVt_REGEXP:
diff --git a/embed.fnc b/embed.fnc
index 5c27b27184..997f42dd1e 100644
--- a/embed.fnc
+++ b/embed.fnc
@@ -1084,8 +1084,8 @@ Ap	|SV*	|regclass_swash	|NULLOK const regexp *prog \
 				|NN const struct regnode *node|bool doinit \
 				|NULLOK SV **listsvp|NULLOK SV **altsvp
 #ifdef PERL_IN_REGCOMP_C
-EMsR	|SV*	|_new_invlist_C_array|NN UV* list
-: Not used currently: EXMs	|bool	|_invlistEQ	|NN SV* const a|NN SV* const b|bool complement_b
+EMsR	|SV*	|_new_invlist_C_array|NN const UV* const list
+: Not used currently: EXMs	|bool	|_invlistEQ	|NN SV* const a|NN SV* const b|const bool complement_b
 #endif
 Ap	|I32	|pregexec	|NN REGEXP * const prog|NN char* stringarg \
 				|NN char* strend|NN char* strbeg|I32 minend \
@@ -1428,7 +1428,7 @@ EsM	|void	|_append_range_to_invlist   |NN SV* const invlist|const UV start|const
 EiMR	|UV*	|_invlist_array_init	|NN SV* const invlist|const bool will_have_0
 EiMR	|UV*	|invlist_array	|NN SV* const invlist
 EsM	|void	|invlist_extend    |NN SV* const invlist|const UV len
-EiMR	|UV*	|get_invlist_zero_addr	|NN SV* invlist
+EiMR	|bool*	|get_invlist_offset_addr|NN SV* invlist
 EiMR	|UV	|invlist_max	|NN SV* const invlist
 EiM	|void	|invlist_set_len|NN SV* const invlist|const UV len
 EiMR	|IV*	|get_invlist_previous_index_addr|NN SV* invlist
@@ -1437,8 +1437,7 @@ EiM	|void	|invlist_set_previous_index|NN SV* const invlist|const IV index
 EiM	|void	|invlist_trim	|NN SV* const invlist
 EiMR	|SV*	|invlist_clone	|NN SV* const invlist
 EiMR	|bool	|invlist_is_iterating|NN SV* const invlist
-EiMR	|UV*	|get_invlist_iter_addr	|NN SV* invlist
-EiMR	|UV*	|get_invlist_version_id_addr	|NN SV* invlist
+EiMR	|STRLEN*|get_invlist_iter_addr	|NN SV* invlist
 EiM	|void	|invlist_iterinit|NN SV* invlist
 EsMR	|bool	|invlist_iternext|NN SV* invlist|NN UV* start|NN UV* end
 EiM	|void	|invlist_iterfinish|NN SV* invlist
@@ -1446,9 +1445,13 @@ EiMR	|UV	|invlist_highest|NN SV* const invlist
 #endif
 #if defined(PERL_IN_REGCOMP_C) || defined(PERL_IN_UTF8_C)
 EXmM	|void	|_invlist_intersection	|NN SV* const a|NN SV* const b|NN SV** i
-EXpM	|void	|_invlist_intersection_maybe_complement_2nd|NULLOK SV* const a|NN SV* const b|bool complement_b|NN SV** i
+EXpM	|void	|_invlist_intersection_maybe_complement_2nd \
+		|NULLOK SV* const a|NN SV* const b          \
+		|const bool complement_b|NN SV** i
 EXmM	|void	|_invlist_union	|NULLOK SV* const a|NN SV* const b|NN SV** output
-EXpM	|void	|_invlist_union_maybe_complement_2nd|NULLOK SV* const a|NN SV* const b|bool complement_b|NN SV** output
+EXpM	|void	|_invlist_union_maybe_complement_2nd        \
+		|NULLOK SV* const a|NN SV* const b          \
+		|const bool complement_b|NN SV** output
 EXmM	|void	|_invlist_subtract|NN SV* const a|NN SV* const b|NN SV** result
 EXpM	|void	|_invlist_invert|NN SV* const invlist
 EXpM	|void	|_invlist_invert_prop|NN SV* const invlist
@@ -1464,7 +1467,7 @@ EXp	|SV*	|_core_swash_init|NN const char* pkg|NN const char* name \
 #endif
 #if defined(PERL_IN_REGCOMP_C) || defined(PERL_IN_REGEXEC_C) || defined(PERL_IN_UTF8_C)
 EXMpR	|SV*	|_invlist_contents|NN SV* const invlist
-EiMR	|UV*	|_get_invlist_len_addr	|NN SV* invlist
+EiMR	|STRLEN*|_get_invlist_len_addr	|NN SV* invlist
 EiMR	|UV	|_invlist_len	|NN SV* const invlist
 EMiR	|bool	|_invlist_contains_cp|NN SV* const invlist|const UV cp
 EXpMR	|IV	|_invlist_search	|NN SV* const invlist|const UV cp
diff --git a/embed.h b/embed.h
index 0666e6f453..c15875598d 100644
--- a/embed.h
+++ b/embed.h
@@ -904,9 +904,8 @@
 #define compute_EXACTish(a)	S_compute_EXACTish(aTHX_ a)
 #define could_it_be_a_POSIX_class(a)	S_could_it_be_a_POSIX_class(aTHX_ a)
 #define get_invlist_iter_addr(a)	S_get_invlist_iter_addr(aTHX_ a)
+#define get_invlist_offset_addr(a)	S_get_invlist_offset_addr(aTHX_ a)
 #define get_invlist_previous_index_addr(a)	S_get_invlist_previous_index_addr(aTHX_ a)
-#define get_invlist_version_id_addr(a)	S_get_invlist_version_id_addr(aTHX_ a)
-#define get_invlist_zero_addr(a)	S_get_invlist_zero_addr(aTHX_ a)
 #define grok_bslash_N(a,b,c,d,e,f,g)	S_grok_bslash_N(aTHX_ a,b,c,d,e,f,g)
 #define handle_regex_sets(a,b,c,d,e)	S_handle_regex_sets(aTHX_ a,b,c,d,e)
 #define invlist_array(a)	S_invlist_array(aTHX_ a)
diff --git a/ext/B/B.xs b/ext/B/B.xs
index fbe6be6719..e7049f04c2 100644
--- a/ext/B/B.xs
+++ b/ext/B/B.xs
@@ -21,13 +21,13 @@ typedef FILE * InputStream;
 
 static const char* const svclassnames[] = {
     "B::NULL",
-    "B::BIND",
     "B::IV",
     "B::NV",
 #if PERL_VERSION <= 10
     "B::RV",
 #endif
     "B::PV",
+    "B::INVLIST",
     "B::PVIV",
     "B::PVNV",
     "B::PVMG",
diff --git a/inline_invlist.c b/inline_invlist.c
index b56ce60002..a29964524b 100644
--- a/inline_invlist.c
+++ b/inline_invlist.c
@@ -8,39 +8,12 @@
 
 #if defined(PERL_IN_UTF8_C) || defined(PERL_IN_REGCOMP_C) || defined(PERL_IN_REGEXEC_C)
 
-#define INVLIST_LEN_OFFSET 0	/* Number of elements in the inversion list */
-#define INVLIST_ITER_OFFSET 1	/* Current iteration position */
-#define INVLIST_PREVIOUS_INDEX_OFFSET 2  /* Place to cache index of previous
-                                            result */
-
-/* This is a combination of a version and data structure type, so that one
- * being passed in can be validated to be an inversion list of the correct
- * vintage.  When the structure of the header is changed, a new random number
- * in the range 2**31-1 should be generated and the new() method changed to
- * insert that at this location.  Then, if an auxiliary program doesn't change
- * correspondingly, it will be discovered immediately */
-#define INVLIST_VERSION_ID_OFFSET 3
-#define INVLIST_VERSION_ID 290655244
-
-/* For safety, when adding new elements, remember to #undef them at the end of
- * the inversion list code section */
-
-#define INVLIST_ZERO_OFFSET 4	/* 0 or 1; must be last element in header */
-/* The UV at position ZERO contains either 0 or 1.  If 0, the inversion list
- * contains the code point U+00000, and begins here.  If 1, the inversion list
- * doesn't contain U+0000, and it begins at the next UV in the array.
- * Inverting an inversion list consists of adding or removing the 0 at the
- * beginning of it.  By reserving a space for that 0, inversion can be made
- * very fast */
-
-#define HEADER_LENGTH (INVLIST_ZERO_OFFSET + 1)
-
 /* An element is in an inversion list iff its index is even numbered: 0, 2, 4,
  * etc */
 #define ELEMENT_RANGE_MATCHES_INVLIST(i) (! ((i) & 1))
 #define PREV_RANGE_MATCHES_INVLIST(i) (! ELEMENT_RANGE_MATCHES_INVLIST(i))
 
-PERL_STATIC_INLINE UV*
+PERL_STATIC_INLINE STRLEN*
 S__get_invlist_len_addr(pTHX_ SV* invlist)
 {
     /* Return the address of the UV that contains the current number
@@ -48,7 +21,7 @@ S__get_invlist_len_addr(pTHX_ SV* invlist)
 
     PERL_ARGS_ASSERT__GET_INVLIST_LEN_ADDR;
 
-    return (UV *) (SvPVX(invlist) + (INVLIST_LEN_OFFSET * sizeof (UV)));
+    return &(((XINVLIST*) SvANY(invlist))->count);
 }
 
 PERL_STATIC_INLINE UV
diff --git a/perl.h b/perl.h
index 0593461272..4bfc8fa21f 100644
--- a/perl.h
+++ b/perl.h
@@ -2278,6 +2278,7 @@ typedef struct xpvuv XPVUV;
 typedef struct xpvnv XPVNV;
 typedef struct xpvmg XPVMG;
 typedef struct xpvlv XPVLV;
+typedef struct xpvinvlist XINVLIST;
 typedef struct xpvav XPVAV;
 typedef struct xpvhv XPVHV;
 typedef struct xpvgv XPVGV;
@@ -5043,19 +5044,19 @@ EXTCONST U8 PL_magic_data[256];
 #endif
 
 #ifdef DOINIT
-		        /* NL BD IV NV PV PI PN MG RX GV LV AV HV CV FM IO */
+		        /* NL IV NV PV INV PI PN MG RX GV LV AV HV CV FM IO */
 EXTCONST bool
-PL_valid_types_IVX[]    = { 0, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0 };
+PL_valid_types_IVX[]    = { 0, 1, 0, 0, 0, 1, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0 };
 EXTCONST bool
-PL_valid_types_NVX[]    = { 0, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0 };
+PL_valid_types_NVX[]    = { 0, 0, 1, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 0 };
 EXTCONST bool
-PL_valid_types_PVX[]    = { 0, 0, 0, 0, 1, 1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1 };
+PL_valid_types_PVX[]    = { 0, 0, 0, 1, 1, 1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 1 };
 EXTCONST bool
-PL_valid_types_RV[]     = { 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1 };
+PL_valid_types_RV[]     = { 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 1 };
 EXTCONST bool
-PL_valid_types_IV_set[] = { 0, 0, 1, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1 };
+PL_valid_types_IV_set[] = { 0, 1, 0, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1 };
 EXTCONST bool
-PL_valid_types_NV_set[] = { 0, 0, 0, 1, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 };
+PL_valid_types_NV_set[] = { 0, 0, 1, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0 };
 
 #else
 
diff --git a/proto.h b/proto.h
index 9a06590ab0..865d57747f 100644
--- a/proto.h
+++ b/proto.h
@@ -6416,7 +6416,7 @@ PERL_STATIC_INLINE UV*	S__invlist_array_init(pTHX_ SV* const invlist, const bool
 #define PERL_ARGS_ASSERT__INVLIST_ARRAY_INIT	\
 	assert(invlist)
 
-STATIC SV*	S__new_invlist_C_array(pTHX_ UV* list)
+STATIC SV*	S__new_invlist_C_array(pTHX_ const UV* const list)
 			__attribute__warn_unused_result__
 			__attribute__nonnull__(pTHX_1);
 #define PERL_ARGS_ASSERT__NEW_INVLIST_C_ARRAY	\
@@ -6480,28 +6480,22 @@ STATIC bool	S_could_it_be_a_POSIX_class(pTHX_ struct RExC_state_t *pRExC_state)
 #define PERL_ARGS_ASSERT_COULD_IT_BE_A_POSIX_CLASS	\
 	assert(pRExC_state)
 
-PERL_STATIC_INLINE UV*	S_get_invlist_iter_addr(pTHX_ SV* invlist)
+PERL_STATIC_INLINE STRLEN*	S_get_invlist_iter_addr(pTHX_ SV* invlist)
 			__attribute__warn_unused_result__
 			__attribute__nonnull__(pTHX_1);
 #define PERL_ARGS_ASSERT_GET_INVLIST_ITER_ADDR	\
 	assert(invlist)
 
-PERL_STATIC_INLINE IV*	S_get_invlist_previous_index_addr(pTHX_ SV* invlist)
-			__attribute__warn_unused_result__
-			__attribute__nonnull__(pTHX_1);
-#define PERL_ARGS_ASSERT_GET_INVLIST_PREVIOUS_INDEX_ADDR	\
-	assert(invlist)
-
-PERL_STATIC_INLINE UV*	S_get_invlist_version_id_addr(pTHX_ SV* invlist)
+PERL_STATIC_INLINE bool*	S_get_invlist_offset_addr(pTHX_ SV* invlist)
 			__attribute__warn_unused_result__
 			__attribute__nonnull__(pTHX_1);
-#define PERL_ARGS_ASSERT_GET_INVLIST_VERSION_ID_ADDR	\
+#define PERL_ARGS_ASSERT_GET_INVLIST_OFFSET_ADDR	\
 	assert(invlist)
 
-PERL_STATIC_INLINE UV*	S_get_invlist_zero_addr(pTHX_ SV* invlist)
+PERL_STATIC_INLINE IV*	S_get_invlist_previous_index_addr(pTHX_ SV* invlist)
 			__attribute__warn_unused_result__
 			__attribute__nonnull__(pTHX_1);
-#define PERL_ARGS_ASSERT_GET_INVLIST_ZERO_ADDR	\
+#define PERL_ARGS_ASSERT_GET_INVLIST_PREVIOUS_INDEX_ADDR	\
 	assert(invlist)
 
 STATIC bool	S_grok_bslash_N(pTHX_ struct RExC_state_t *pRExC_state, regnode** nodep, UV *valuep, I32 *flagp, U32 depth, bool in_char_class, const bool strict)
@@ -6743,7 +6737,7 @@ STATIC I32	S_study_chunk(pTHX_ struct RExC_state_t *pRExC_state, regnode **scanp
 
 #endif
 #if defined(PERL_IN_REGCOMP_C) || defined(PERL_IN_REGEXEC_C) || defined(PERL_IN_UTF8_C)
-PERL_STATIC_INLINE UV*	S__get_invlist_len_addr(pTHX_ SV* invlist)
+PERL_STATIC_INLINE STRLEN*	S__get_invlist_len_addr(pTHX_ SV* invlist)
 			__attribute__warn_unused_result__
 			__attribute__nonnull__(pTHX_1);
 #define PERL_ARGS_ASSERT__GET_INVLIST_LEN_ADDR	\
@@ -6839,7 +6833,7 @@ PERL_CALLCONV SV*	Perl__add_range_to_invlist(pTHX_ SV* invlist, const UV start,
 			__attribute__nonnull__(pTHX_2)
 			__attribute__nonnull__(pTHX_3); */
 
-PERL_CALLCONV void	Perl__invlist_intersection_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, bool complement_b, SV** i)
+PERL_CALLCONV void	Perl__invlist_intersection_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, const bool complement_b, SV** i)
 			__attribute__nonnull__(pTHX_2)
 			__attribute__nonnull__(pTHX_4);
 #define PERL_ARGS_ASSERT__INVLIST_INTERSECTION_MAYBE_COMPLEMENT_2ND	\
@@ -6870,7 +6864,7 @@ PERL_CALLCONV void	Perl__invlist_populate_swatch(pTHX_ SV* const invlist, const
 			__attribute__nonnull__(pTHX_2)
 			__attribute__nonnull__(pTHX_3); */
 
-PERL_CALLCONV void	Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, bool complement_b, SV** output)
+PERL_CALLCONV void	Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, const bool complement_b, SV** output)
 			__attribute__nonnull__(pTHX_2)
 			__attribute__nonnull__(pTHX_4);
 #define PERL_ARGS_ASSERT__INVLIST_UNION_MAYBE_COMPLEMENT_2ND	\
diff --git a/regcomp.c b/regcomp.c
index 4885c0b5a6..db6f2d445a 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -7026,11 +7026,12 @@ S_reg_scan_name(pTHX_ RExC_state_t *pRExC_state, U32 flags)
 /* This section of code defines the inversion list object and its methods.  The
  * interfaces are highly subject to change, so as much as possible is static to
  * this file.  An inversion list is here implemented as a malloc'd C UV array
- * with some added info that is placed as UVs at the beginning in a header
- * portion.  An inversion list for Unicode is an array of code points, sorted
- * by ordinal number.  The zeroth element is the first code point in the list.
- * The 1th element is the first element beyond that not in the list.  In other
- * words, the first range is
+ * as an SVt_INVLIST scalar.
+ *
+ * An inversion list for Unicode is an array of code points, sorted by ordinal
+ * number.  The zeroth element is the first code point in the list.  The 1th
+ * element is the first element beyond that not in the list.  In other words,
+ * the first range is
  *  invlist[0]..(invlist[1]-1)
  * The other ranges follow.  Thus every element whose index is divisible by two
  * marks the beginning of a range that is in the list, and every element not
@@ -7047,10 +7048,10 @@ S_reg_scan_name(pTHX_ RExC_state_t *pRExC_state, U32 flags)
  * list.)
  * Taking the complement (inverting) an inversion list is quite simple, if the
  * first element is 0, remove it; otherwise add a 0 element at the beginning.
- * This implementation reserves an element at the beginning of each inversion
- * list to contain 0 when the list contains 0, and contains 1 otherwise.  The
- * actual beginning of the list is either that element if 0, or the next one if
- * 1.
+ * This implementation reserves an element (considered to be the final element
+ * of the header) at the beginning of each inversion list to always contain 0;
+ * there is an additional flag in the header which indicates if the list begins
+ * at the 0, or is offset to begin at the next element.
  *
  * More about inversion lists can be found in "Unicode Demystified"
  * Chapter 13 by Richard Gillam, published by Addison-Wesley.
@@ -7065,32 +7066,39 @@ S_reg_scan_name(pTHX_ RExC_state_t *pRExC_state, U32 flags)
  * should eventually be made public */
 
 /* The header definitions are in F<inline_invlist.c> */
-#define TO_INTERNAL_SIZE(x) (((x) + HEADER_LENGTH) * sizeof(UV))
-#define FROM_INTERNAL_SIZE(x) (((x)/ sizeof(UV)) - HEADER_LENGTH)
 
-#define INVLIST_INITIAL_LEN 10
+/* This converts to/from our UVs to what the SV code is expecting: bytes.  The
+ * first element is always a 0, which may or may not currently be in the list.
+ * Just assume the worst case, that it isn't, and so the length of the list
+ * passed in has to add 1 to account for it */
+#define TO_INTERNAL_SIZE(x) (((x) + 1) * sizeof(UV))
+#define FROM_INTERNAL_SIZE(x) (((x)/ sizeof(UV)) - 1)
+
 
 PERL_STATIC_INLINE UV*
 S__invlist_array_init(pTHX_ SV* const invlist, const bool will_have_0)
 {
     /* Returns a pointer to the first element in the inversion list's array.
      * This is called upon initialization of an inversion list.  Where the
-     * array begins depends on whether the list has the code point U+0000
-     * in it or not.  The other parameter tells it whether the code that
-     * follows this call is about to put a 0 in the inversion list or not.
-     * The first element is either the element with 0, if 0, or the next one,
-     * if 1 */
+     * array begins depends on whether the list has the code point U+0000 in it
+     * or not.  The other parameter tells it whether the code that follows this
+     * call is about to put a 0 in the inversion list or not.  The first
+     * element is either the element reserved for 0, if TRUE, or the element
+     * after it, if FALSE */
 
-    UV* zero = get_invlist_zero_addr(invlist);
+    bool* offset = get_invlist_offset_addr(invlist);
+    UV* zero_addr = (UV *) SvPVX(invlist);
 
     PERL_ARGS_ASSERT__INVLIST_ARRAY_INIT;
 
     /* Must be empty */
     assert(! *_get_invlist_len_addr(invlist));
 
+    *zero_addr = 0;
+
     /* 1^1 = 0; 1^0 = 1 */
-    *zero = 1 ^ will_have_0;
-    return zero + *zero;
+    *offset = 1 ^ will_have_0;
+    return zero_addr + *offset;
 }
 
 PERL_STATIC_INLINE UV*
@@ -7105,14 +7113,15 @@ S_invlist_array(pTHX_ SV* const invlist)
     /* Must not be empty.  If these fail, you probably didn't check for <len>
      * being non-zero before trying to get the array */
     assert(*_get_invlist_len_addr(invlist));
-    assert(*get_invlist_zero_addr(invlist) == 0
-	   || *get_invlist_zero_addr(invlist) == 1);
-
-    /* The array begins either at the element reserved for zero if the
-     * list contains 0 (that element will be set to 0), or otherwise the next
-     * element (in which case the reserved element will be set to 1). */
-    return (UV *) (get_invlist_zero_addr(invlist)
-		   + *get_invlist_zero_addr(invlist));
+    assert(*get_invlist_offset_addr(invlist) == 0
+	   || *get_invlist_offset_addr(invlist) == 1);
+
+    /* The very first element always contains zero, The array begins either
+     * there, or if the inversion list is offset, at the element after it.
+     * The offset header field determines which; it contains 0 or 1 to indicate
+     * how much additionally to add */
+    assert(0 == *(SvPVX(invlist)));
+    return ((UV *) SvPVX(invlist) + *get_invlist_offset_addr(invlist));
 }
 
 PERL_STATIC_INLINE void
@@ -7124,33 +7133,21 @@ S_invlist_set_len(pTHX_ SV* const invlist, const UV len)
 
     *_get_invlist_len_addr(invlist) = len;
 
-    assert(len <= SvLEN(invlist));
+    assert(SvLEN(invlist) == 0 || len <= SvLEN(invlist));
 
     SvCUR_set(invlist, TO_INTERNAL_SIZE(len));
-    /* If the list contains U+0000, that element is part of the header,
-     * and should not be counted as part of the array.  It will contain
-     * 0 in that case, and 1 otherwise.  So we could flop 0=>1, 1=>0 and
-     * subtract:
-     *	SvCUR_set(invlist,
-     *		  TO_INTERNAL_SIZE(len
-     *				   - (*get_invlist_zero_addr(inv_list) ^ 1)));
-     * But, this is only valid if len is not 0.  The consequences of not doing
-     * this is that the memory allocation code may think that 1 more UV is
-     * being used than actually is, and so might do an unnecessary grow.  That
-     * seems worth not bothering to make this the precise amount.
-     *
-     * Note that when inverting, SvCUR shouldn't change */
+    /* Note that when inverting, SvCUR shouldn't change */
 }
 
 PERL_STATIC_INLINE IV*
 S_get_invlist_previous_index_addr(pTHX_ SV* invlist)
 {
-    /* Return the address of the UV that is reserved to hold the cached index
+    /* Return the address of the IV that is reserved to hold the cached index
      * */
 
     PERL_ARGS_ASSERT_GET_INVLIST_PREVIOUS_INDEX_ADDR;
 
-    return (IV *) (SvPVX(invlist) + (INVLIST_PREVIOUS_INDEX_OFFSET * sizeof (UV)));
+    return &(((XINVLIST*) SvANY(invlist))->prev_index);
 }
 
 PERL_STATIC_INLINE IV
@@ -7188,17 +7185,15 @@ S_invlist_max(pTHX_ SV* const invlist)
            : FROM_INTERNAL_SIZE(SvLEN(invlist));
 }
 
-PERL_STATIC_INLINE UV*
-S_get_invlist_zero_addr(pTHX_ SV* invlist)
+PERL_STATIC_INLINE bool*
+S_get_invlist_offset_addr(pTHX_ SV* invlist)
 {
-    /* Return the address of the UV that is reserved to hold 0 if the inversion
-     * list contains 0.  This has to be the last element of the heading, as the
-     * list proper starts with either it if 0, or the next element if not.
-     * (But we force it to contain either 0 or 1) */
+    /* Return the address of the field that says whether the inversion list is
+     * offset (it contains 1) or not (contains 0) */
 
-    PERL_ARGS_ASSERT_GET_INVLIST_ZERO_ADDR;
+    PERL_ARGS_ASSERT_GET_INVLIST_OFFSET_ADDR;
 
-    return (UV *) (SvPVX(invlist) + (INVLIST_ZERO_OFFSET * sizeof (UV)));
+    return &(((XINVLIST*) SvANY(invlist))->is_offset);
 }
 
 #ifndef PERL_IN_XSUB_RE
@@ -7211,58 +7206,85 @@ Perl__new_invlist(pTHX_ IV initial_size)
      * system default is used instead */
 
     SV* new_list;
+    bool* offset_addr;
 
     if (initial_size < 0) {
-	initial_size = INVLIST_INITIAL_LEN;
+	initial_size = 10;
     }
 
     /* Allocate the initial space */
-    new_list = newSV(TO_INTERNAL_SIZE(initial_size));
+    new_list = newSV_type(SVt_INVLIST);
+    SvGROW(new_list, TO_INTERNAL_SIZE(initial_size) + 1); /* 1 is for trailing
+                                                             NUL */
     invlist_set_len(new_list, 0);
 
     /* Force iterinit() to be used to get iteration to work */
-    *get_invlist_iter_addr(new_list) = UV_MAX;
+    *get_invlist_iter_addr(new_list) = (STRLEN) UV_MAX;
 
     /* This should force a segfault if a method doesn't initialize this
-     * properly */
-    *get_invlist_zero_addr(new_list) = UV_MAX;
+     * properly.  XXX Although now that the max is currently just 255, it might
+     * not segfault. */
+    offset_addr = get_invlist_offset_addr(new_list);
+    *offset_addr = (U8) UV_MAX;
 
     *get_invlist_previous_index_addr(new_list) = 0;
-    *get_invlist_version_id_addr(new_list) = INVLIST_VERSION_ID;
-#if HEADER_LENGTH != 5
-#   error Need to regenerate INVLIST_VERSION_ID by running perl -E 'say int(rand 2**31-1)', and then changing the #if to the new length
-#endif
 
     return new_list;
 }
 #endif
 
 STATIC SV*
-S__new_invlist_C_array(pTHX_ UV* list)
+S__new_invlist_C_array(pTHX_ const UV* const list)
 {
     /* Return a pointer to a newly constructed inversion list, initialized to
      * point to <list>, which has to be in the exact correct inversion list
      * form, including internal fields.  Thus this is a dangerous routine that
-     * should not be used in the wrong hands */
+     * should not be used in the wrong hands.  The passed in 'list' contains
+     * several header fields at the beginning that are not part of the
+     * inversion list body proper */
+
+    const STRLEN length = (STRLEN) list[0];
+    const UV version_id =          list[1];
+    const U8 offset = (U8)         list[2];
+#define HEADER_LENGTH 3
+    /* If any of the above changes in any way, you must change HEADER_LENGTH
+     * (if appropriate) and regenerate INVLIST_VERSION_ID by running
+     *      perl -E 'say int(rand 2**31-1)'
+     */
+#define INVLIST_VERSION_ID 1826693541/* This is a combination of a version and
+                                        data structure type, so that one being
+                                        passed in can be validated to be an
+                                        inversion list of the correct vintage.
+                                       */
 
-    SV* invlist = newSV_type(SVt_PV);
+    SV* invlist = newSV_type(SVt_INVLIST);
 
     PERL_ARGS_ASSERT__NEW_INVLIST_C_ARRAY;
 
-    SvPV_set(invlist, (char *) list);
-    SvLEN_set(invlist, 0);  /* Means we own the contents, and the system
-			       shouldn't touch it */
-    SvCUR_set(invlist, TO_INTERNAL_SIZE(_invlist_len(invlist)));
-
-    if (*get_invlist_version_id_addr(invlist) != INVLIST_VERSION_ID) {
+    if (version_id != INVLIST_VERSION_ID) {
         Perl_croak(aTHX_ "panic: Incorrect version for previously generated inversion list");
     }
 
-    /* Initialize the iteration pointer.
-     * XXX This could be done at compile time in charclass_invlists.h, but I
-     * (khw) am not confident that the suffixes for specifying the C constant
-     * UV_MAX are portable, e.g.  'ull' on a 32 bit machine that is configured
-     * to use 64 bits; might need a Configure probe */
+    /* The generated array passed in includes header elements that aren't part
+     * of the list proper, so start it just after them */
+    SvPV_set(invlist, (char *) (list + HEADER_LENGTH));
+
+    SvLEN_set(invlist, 0);  /* Means we own the contents, and the system
+			       shouldn't touch it */
+    /* The 'length' passed to us is the number of elements in the inversion
+     * list.  If the list doesn't include the always present 0 element, the
+     * length should be adjusted upwards to include it.  The TO_INTERNAL_SIZE
+     * macro returns a worst case scenario, always making that adjustment, even
+     * if not needed.  To get the precise size, then, we have to subtract 1
+     * when that adjustment wasn't needed.  That happens when the offset was 0;
+     * the exclusive-or flips the 0 to 1, and vice versa */
+    SvCUR_set(invlist, TO_INTERNAL_SIZE(length - (offset ^ 1)));
+
+    invlist_set_len(invlist, length);
+    *(get_invlist_offset_addr(invlist)) = offset;
+    invlist_set_previous_index(invlist, 0);
+
+    /* Initialize the iteration pointer. */
     invlist_iterfinish(invlist);
 
     return invlist;
@@ -7554,7 +7576,7 @@ Perl__invlist_populate_swatch(pTHX_ SV* const invlist, const UV start, const UV
 }
 
 void
-Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, bool complement_b, SV** output)
+Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, const bool complement_b, SV** output)
 {
     /* Take the union of two inversion lists and point <output> to it.  *output
      * SHOULD BE DEFINED upon input, and if it points to one of the two lists,
@@ -7576,8 +7598,8 @@ Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, bool co
      * return the larger of the input lists, but then outside code might need
      * to keep track of whether to free the input list or not */
 
-    UV* array_a;    /* a's array */
-    UV* array_b;
+    const UV* array_a;    /* a's array */
+    const UV* array_b;
     UV len_a;	    /* length of a's array */
     UV len_b;
 
@@ -7645,23 +7667,17 @@ Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, bool co
     if (complement_b) {
 
 	/* To complement, we invert: if the first element is 0, remove it.  To
-	 * do this, we just pretend the array starts one later, and clear the
-	 * flag as we don't have to do anything else later */
+	 * do this, we just pretend the array starts one later */
         if (array_b[0] == 0) {
             array_b++;
             len_b--;
-            complement_b = FALSE;
         }
         else {
 
-            /* But if the first element is not zero, we unshift a 0 before the
-             * array.  The data structure reserves a space for that 0 (which
-             * should be a '1' right now), so physical shifting is unneeded,
-             * but temporarily change that element to 0.  Before exiting the
-             * routine, we must restore the element to '1' */
+            /* But if the first element is not zero, we pretend the list starts
+             * at the 0 that is always stored immediately before the array. */
             array_b--;
             len_b++;
-            array_b[0] = 0;
         }
     }
 
@@ -7778,11 +7794,6 @@ Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, bool co
 	}
     }
 
-    /* If we've changed b, restore it */
-    if (complement_b) {
-        array_b[0] = 1;
-    }
-
     /*  We may be removing a reference to one of the inputs */
     if (a == *output || b == *output) {
         assert(! invlist_is_iterating(*output));
@@ -7794,7 +7805,7 @@ Perl__invlist_union_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, bool co
 }
 
 void
-Perl__invlist_intersection_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, bool complement_b, SV** i)
+Perl__invlist_intersection_maybe_complement_2nd(pTHX_ SV* const a, SV* const b, const bool complement_b, SV** i)
 {
     /* Take the intersection of two inversion lists and point <i> to it.  *i
      * SHOULD BE DEFINED upon input, and if it points to one of the two lists,
@@ -7811,8 +7822,8 @@ Perl__invlist_intersection_maybe_complement_2nd(pTHX_ SV* const a, SV* const b,
      * union above
      */
 
-    UV* array_a;		/* a's array */
-    UV* array_b;
+    const UV* array_a;		/* a's array */
+    const UV* array_b;
     UV len_a;	/* length of a's array */
     UV len_b;
 
@@ -7877,23 +7888,17 @@ Perl__invlist_intersection_maybe_complement_2nd(pTHX_ SV* const a, SV* const b,
     if (complement_b) {
 
 	/* To complement, we invert: if the first element is 0, remove it.  To
-	 * do this, we just pretend the array starts one later, and clear the
-	 * flag as we don't have to do anything else later */
+	 * do this, we just pretend the array starts one later */
         if (array_b[0] == 0) {
             array_b++;
             len_b--;
-            complement_b = FALSE;
         }
         else {
 
-            /* But if the first element is not zero, we unshift a 0 before the
-             * array.  The data structure reserves a space for that 0 (which
-             * should be a '1' right now), so physical shifting is unneeded,
-             * but temporarily change that element to 0.  Before exiting the
-             * routine, we must restore the element to '1' */
+            /* But if the first element is not zero, we pretend the list starts
+             * at the 0 that is always stored immediately before the array. */
             array_b--;
             len_b++;
-            array_b[0] = 0;
         }
     }
 
@@ -8000,11 +8005,6 @@ Perl__invlist_intersection_maybe_complement_2nd(pTHX_ SV* const a, SV* const b,
 	}
     }
 
-    /* If we've changed b, restore it */
-    if (complement_b) {
-        array_b[0] = 1;
-    }
-
     /*  We may be removing a reference to one of the inputs */
     if (a == *i || b == *i) {
         assert(! invlist_is_iterating(*i));
@@ -8073,7 +8073,7 @@ Perl__invlist_invert(pTHX_ SV* const invlist)
      * have a zero; removes it otherwise.  As described above, the data
      * structure is set up so that this is very efficient */
 
-    UV* len_pos = _get_invlist_len_addr(invlist);
+    STRLEN* len_pos = _get_invlist_len_addr(invlist);
 
     PERL_ARGS_ASSERT__INVLIST_INVERT;
 
@@ -8088,7 +8088,7 @@ Perl__invlist_invert(pTHX_ SV* const invlist)
     /* The exclusive or complents 0 to 1; and 1 to 0.  If the result is 1, the
      * zero element was a 0, so it is being removed, so the length decrements
      * by 1; and vice-versa.  SvCUR is unaffected */
-    if (*get_invlist_zero_addr(invlist) ^= 1) {
+    if (*get_invlist_offset_addr(invlist) ^= 1) {
 	(*len_pos)--;
     }
     else {
@@ -8150,12 +8150,15 @@ S_invlist_clone(pTHX_ SV* const invlist)
     PERL_ARGS_ASSERT_INVLIST_CLONE;
 
     SvCUR_set(new_invlist, length); /* This isn't done automatically */
+    invlist_set_len(new_invlist, _invlist_len(invlist));
+    *(get_invlist_offset_addr(new_invlist))
+                                = *(get_invlist_offset_addr(invlist));
     Copy(SvPVX(invlist), SvPVX(new_invlist), length, char);
 
     return new_invlist;
 }
 
-PERL_STATIC_INLINE UV*
+PERL_STATIC_INLINE STRLEN*
 S_get_invlist_iter_addr(pTHX_ SV* invlist)
 {
     /* Return the address of the UV that contains the current iteration
@@ -8163,17 +8166,7 @@ S_get_invlist_iter_addr(pTHX_ SV* invlist)
 
     PERL_ARGS_ASSERT_GET_INVLIST_ITER_ADDR;
 
-    return (UV *) (SvPVX(invlist) + (INVLIST_ITER_OFFSET * sizeof (UV)));
-}
-
-PERL_STATIC_INLINE UV*
-S_get_invlist_version_id_addr(pTHX_ SV* invlist)
-{
-    /* Return the address of the UV that contains the version id. */
-
-    PERL_ARGS_ASSERT_GET_INVLIST_VERSION_ID_ADDR;
-
-    return (UV *) (SvPVX(invlist) + (INVLIST_VERSION_ID_OFFSET * sizeof (UV)));
+    return &(((XINVLIST*) SvANY(invlist))->iterator);
 }
 
 PERL_STATIC_INLINE void
@@ -8197,7 +8190,7 @@ S_invlist_iterfinish(pTHX_ SV* invlist)
 
     PERL_ARGS_ASSERT_INVLIST_ITERFINISH;
 
-    *get_invlist_iter_addr(invlist) = UV_MAX;
+    *get_invlist_iter_addr(invlist) = (STRLEN) UV_MAX;
 }
 
 STATIC bool
@@ -8210,14 +8203,14 @@ S_invlist_iternext(pTHX_ SV* invlist, UV* start, UV* end)
      * <*start> and <*end> are unchanged, and the next call to this function
      * will start over at the beginning of the list */
 
-    UV* pos = get_invlist_iter_addr(invlist);
+    STRLEN* pos = get_invlist_iter_addr(invlist);
     UV len = _invlist_len(invlist);
     UV *array;
 
     PERL_ARGS_ASSERT_INVLIST_ITERNEXT;
 
     if (*pos >= len) {
-	*pos = UV_MAX;	/* Force iterinit() to be required next time */
+	*pos = (STRLEN) UV_MAX;	/* Force iterinit() to be required next time */
 	return FALSE;
     }
 
@@ -8240,7 +8233,7 @@ S_invlist_is_iterating(pTHX_ SV* const invlist)
 {
     PERL_ARGS_ASSERT_INVLIST_IS_ITERATING;
 
-    return *(get_invlist_iter_addr(invlist)) < UV_MAX;
+    return *(get_invlist_iter_addr(invlist)) < (STRLEN) UV_MAX;
 }
 
 PERL_STATIC_INLINE UV
@@ -8343,14 +8336,14 @@ Perl__invlist_dump(pTHX_ SV* const invlist, const char * const header)
 
 #if 0
 bool
-S__invlistEQ(pTHX_ SV* const a, SV* const b, bool complement_b)
+S__invlistEQ(pTHX_ SV* const a, SV* const b, const bool complement_b)
 {
     /* Return a boolean as to if the two passed in inversion lists are
      * identical.  The final argument, if TRUE, says to take the complement of
      * the second inversion list before doing the comparison */
 
-    UV* array_a = invlist_array(a);
-    UV* array_b = invlist_array(b);
+    const UV* array_a = invlist_array(a);
+    const UV* array_b = invlist_array(b);
     UV len_a = _invlist_len(a);
     UV len_b = _invlist_len(b);
 
@@ -8372,20 +8365,15 @@ S__invlistEQ(pTHX_ SV* const a, SV* const b, bool complement_b)
 
             /* Otherwise, to complement, we invert.  Here, the first element is
              * 0, just remove it.  To do this, we just pretend the array starts
-             * one later, and clear the flag as we don't have to do anything
-             * else later */
+             * one later */
 
             array_b++;
             len_b--;
-            complement_b = FALSE;
         }
         else {
 
-            /* But if the first element is not zero, we unshift a 0 before the
-             * array.  The data structure reserves a space for that 0 (which
-             * should be a '1' right now), so physical shifting is unneeded,
-             * but temporarily change that element to 0.  Before exiting the
-             * routine, we must restore the element to '1' */
+            /* But if the first element is not zero, we pretend the list starts
+             * at the 0 that is always stored immediately before the array. */
             array_b--;
             len_b++;
             array_b[0] = 0;
@@ -8405,22 +8393,14 @@ S__invlistEQ(pTHX_ SV* const a, SV* const b, bool complement_b)
         }
     }
 
-    if (complement_b) {
-        array_b[0] = 1;
-    }
     return retval;
 }
 #endif
 
 #undef HEADER_LENGTH
-#undef INVLIST_INITIAL_LENGTH
 #undef TO_INTERNAL_SIZE
 #undef FROM_INTERNAL_SIZE
-#undef INVLIST_LEN_OFFSET
-#undef INVLIST_ZERO_OFFSET
-#undef INVLIST_ITER_OFFSET
 #undef INVLIST_VERSION_ID
-#undef INVLIST_PREVIOUS_INDEX_OFFSET
 
 /* End of inversion list object */
 
diff --git a/regen/mk_invlists.pl b/regen/mk_invlists.pl
index 67b6e417fc..5163907e60 100644
--- a/regen/mk_invlists.pl
+++ b/regen/mk_invlists.pl
@@ -15,7 +15,7 @@ require 'regen/regen_lib.pl';
 # in the headers is used to minimize the possibility of things getting
 # out-of-sync, or the wrong data structure being passed.  Currently that
 # random number is:
-my $VERSION_DATA_STRUCTURE_TYPE = 290655244;
+my $VERSION_DATA_STRUCTURE_TYPE = 1826693541;
 
 my $out_fh = open_new('charclass_invlists.h', '>',
 		      {style => '*', by => $0,
@@ -36,37 +36,22 @@ sub output_invlist ($$) {
     # Output the inversion list $invlist using the name $name for it.
     # It is output in the exact internal form for inversion lists.
 
-    my $zero_or_one;    # Is the last element of the header 0, or 1 ?
-
-    # If the first element is 0, it goes in the header, instead of the body
-    if ($invlist->[0] == 0) {
-        shift @$invlist;
-
-        $zero_or_one = 0;
-
-        # Add a dummy 0 at the end so that the length is constant.  inversion
-        # lists are always stored with enough room so that if they change from
-        # beginning with 0, they don't have to grow.
-        push @$invlist, 0;
-    }
-    else {
+    # Is the last element of the header 0, or 1 ?
+    my $zero_or_one = 0;
+    my $count = @$invlist;
+    if ($invlist->[0] != 0) {
+        unshift @$invlist, 0;
         $zero_or_one = 1;
     }
 
     print $out_fh "\n#ifndef PERL_IN_XSUB_RE\n" unless exists $include_in_ext_re{$name};
-    print $out_fh "\nstatic UV ${name}_invlist[] = {\n";
-
-    print $out_fh "\t", scalar @$invlist, ",\t/* Number of elements */\n";
+    print $out_fh "\nstatic const UV ${name}_invlist[] = {\n";
 
-    # This should be UV_MAX, but I (khw) am not confident that the suffixes
-    # for specifying the constant are portable, e.g.  'ull' on a 32 bit
-    # machine that is configured to use 64 bits; might need a Configure probe
-    print $out_fh "\t0,\t/* Current iteration position */\n";
-    print $out_fh "\t0,\t/* Cache of previous search index result */\n";
+    print $out_fh "\t$count,\t/* Number of elements */\n";
     print $out_fh "\t$VERSION_DATA_STRUCTURE_TYPE, /* Version and data structure type */\n";
     print $out_fh "\t", $zero_or_one,
-                  ",\t/* 0 if this is the first element of the list proper;",
-                  "\n\t\t   1 if the next element is the first */\n";
+                  ",\t/* 0 if the list starts at 0;",
+                  "\n\t\t   1 if it starts at the element beyond 0 */\n";
 
     # The main body are the UVs passed in to this routine.  Do the final
     # element separately
diff --git a/sv.c b/sv.c
index ec70030886..8d23a3a678 100644
--- a/sv.c
+++ b/sv.c
@@ -881,11 +881,6 @@ static const struct body_details bodies_by_type[] = {
     /* HEs use this offset for their arena.  */
     { 0, 0, 0, SVt_NULL, FALSE, NONV, NOARENA, 0 },
 
-    /* The bind placeholder pretends to be an RV for now.
-       Also it's marked as "can't upgrade" to stop anyone using it before it's
-       implemented.  */
-    { 0, 0, 0, SVt_DUMMY, TRUE, NONV, NOARENA, 0 },
-
     /* IVs are in the head, so the allocation size is 0.  */
     { 0,
       sizeof(IV), /* This is used to copy out the IV body.  */
@@ -903,6 +898,12 @@ static const struct body_details bodies_by_type[] = {
       SVt_PV, FALSE, NONV, HASARENA,
       FIT_ARENA(0, sizeof(XPV) - STRUCT_OFFSET(XPV, xpv_cur)) },
 
+    { sizeof(XINVLIST) - STRUCT_OFFSET(XPV, xpv_cur),
+      copy_length(XINVLIST, is_offset) - STRUCT_OFFSET(XPV, xpv_cur),
+      + STRUCT_OFFSET(XPV, xpv_cur),
+      SVt_INVLIST, TRUE, NONV, HASARENA,
+      FIT_ARENA(0, sizeof(XINVLIST) - STRUCT_OFFSET(XPV, xpv_cur)) },
+
     { sizeof(XPVIV) - STRUCT_OFFSET(XPV, xpv_cur),
       copy_length(XPVIV, xiv_u) - STRUCT_OFFSET(XPV, xpv_cur),
       + STRUCT_OFFSET(XPV, xpv_cur),
@@ -1340,6 +1341,7 @@ Perl_sv_upgrade(pTHX_ SV *const sv, svtype new_type)
     case SVt_PVGV:
     case SVt_PVCV:
     case SVt_PVLV:
+    case SVt_INVLIST:
     case SVt_REGEXP:
     case SVt_PVMG:
     case SVt_PVNV:
@@ -4117,7 +4119,7 @@ Perl_sv_setsv_flags(pTHX_ SV *dstr, SV* sstr, const I32 flags)
 	}
 	break;
 
-	/* case SVt_DUMMY: */
+	case SVt_INVLIST:
     case SVt_PVLV:
     case SVt_PVGV:
     case SVt_PVMG:
@@ -6178,7 +6180,7 @@ Perl_sv_clear(pTHX_ SV *const orig_sv)
 		SvREFCNT_dec(SvSTASH(sv));
 	}
 	switch (type) {
-	    /* case SVt_DUMMY: */
+	    /* case SVt_INVLIST: */
 	case SVt_PVIO:
 	    if (IoIFP(sv) &&
 		IoIFP(sv) != PerlIO_stdin() &&
@@ -6304,6 +6306,7 @@ Perl_sv_clear(pTHX_ SV *const orig_sv)
 	case SVt_PVMG:
 	case SVt_PVNV:
 	case SVt_PVIV:
+	case SVt_INVLIST:
 	case SVt_PV:
 	  freescalar:
 	    /* Don't bother with SvOOK_off(sv); as we're only going to
@@ -9440,7 +9443,7 @@ Perl_sv_reftype(pTHX_ const SV *const sv, const int ob)
 				    ? "GLOB" : "SCALAR");
 	case SVt_PVFM:		return "FORMAT";
 	case SVt_PVIO:		return "IO";
-	case SVt_DUMMY:		return "DUMMY";
+	case SVt_INVLIST:	return "INVLIST";
 	case SVt_REGEXP:	return "REGEXP";
 	default:		return "UNKNOWN";
 	}
@@ -12177,7 +12180,6 @@ S_sv_dup_common(pTHX_ const SV *const sstr, CLONE_PARAMS *const param)
 	SvANY(dstr)	= new_XNV();
 	SvNV_set(dstr, SvNVX(sstr));
 	break;
-	/* case SVt_DUMMY: */
     default:
 	{
 	    /* These are all the types that need complex bodies allocating.  */
@@ -12202,6 +12204,7 @@ S_sv_dup_common(pTHX_ const SV *const sstr, CLONE_PARAMS *const param)
 	    case SVt_PVMG:
 	    case SVt_PVNV:
 	    case SVt_PVIV:
+            case SVt_INVLIST:
 	    case SVt_PV:
 		assert(sv_type_details->body_size);
 		if (sv_type_details->arena) {
diff --git a/sv.h b/sv.h
index 0c1ded6a13..c2be3ba81d 100644
--- a/sv.h
+++ b/sv.h
@@ -29,6 +29,7 @@ The types are:
     SVt_PVIV
     SVt_PVNV
     SVt_PVMG
+    SVt_INVLIST
     SVt_REGEXP
     SVt_PVGV
     SVt_PVLV
@@ -56,7 +57,8 @@ typeglob has been assigned.  Assigning to it again will stop it from being
 a typeglob.  SVt_PVLV represents a scalar that delegates to another scalar
 behind the scenes.  It is used, e.g., for the return value of C<substr> and
 for tied hash and array elements.  It can hold any scalar value, including
-a typeglob. SVt_REGEXP is for regular expressions.
+a typeglob. SVt_REGEXP is for regular expressions.  SVt_INVLIST is for Perl
+core internal use only.
 
 SVt_PVMG represents a "normal" scalar (not a typeglob, regular expression,
 or delegate).  Since most scalars do not need all the internal fields of a
@@ -90,6 +92,9 @@ Type flag for scalars.  See L</svtype>.
 =for apidoc AmU||SVt_PVMG
 Type flag for scalars.  See L</svtype>.
 
+=for apidoc AmU||SVt_INVLIST
+Type flag for scalars.  See L</svtype>.
+
 =for apidoc AmU||SVt_REGEXP
 Type flag for regular expressions.  See L</svtype>.
 
@@ -119,11 +124,12 @@ Type flag for I/O objects.  See L</svtype>.
 
 typedef enum {
 	SVt_NULL,	/* 0 */
-	SVt_DUMMY,	/* 1 */
-	SVt_IV,		/* 2 */
-	SVt_NV,		/* 3 */
+	/* BIND was here, before INVLIST replaced it.  */
+	SVt_IV,		/* 1 */
+	SVt_NV,		/* 2 */
 	/* RV was here, before it was merged with IV.  */
-	SVt_PV,		/* 4 */
+	SVt_PV,		/* 3 */
+	SVt_INVLIST,	/* 4, implemented as a PV */
 	SVt_PVIV,	/* 5 */
 	SVt_PVNV,	/* 6 */
 	SVt_PVMG,	/* 7 */
@@ -140,7 +146,9 @@ typedef enum {
 } svtype;
 
 /* *** any alterations to the SV types above need to be reflected in
- * SVt_MASK and the various PL_valid_types_* tables */
+ * SVt_MASK and the various PL_valid_types_* tables.  As of this writing those
+ * tables are in perl.h.  There are also two affected names tables in dump.c,
+ * one in B.xs, and 'bodies_by_type[]' in sv.c */
 
 #define SVt_MASK 0xf	/* smallest bitmask that covers all types */
 
@@ -520,6 +528,14 @@ struct xpvlv {
     char	xlv_flags;	/* 1 = negative offset  2 = negative len */
 };
 
+struct xpvinvlist {
+    _XPV_HEAD;
+    IV          prev_index;
+    STRLEN	iterator;
+    STRLEN	count;
+    bool	is_offset;	/* */
+};
+
 /* This structure works in 3 ways - regular scalar, GV with GP, or fast
    Boyer-Moore.  */
 struct xpvgv {