HINT_UTF8 is not propagated to the op tree anymore; add a

perlunicode.pod that reflects changes to unicode support so far

p4raw-id: //depot/perl@4941

12 files changed, 284 insertions, 149 deletions

diff --git a/MANIFEST b/MANIFEST
index 7d248e5720..a6506d85ce 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -1104,6 +1104,7 @@ pod/perltodo.pod	Todo list explained
 pod/perltoot.pod	Tom's object-oriented tutorial
 pod/perltootc.pod	Tom's object-oriented tutorial (more on class data)
 pod/perltrap.pod	Trap info
+pod/perlunicode.pod	Unicode support info
 pod/perlvar.pod		Variable info
 pod/perlxs.pod		XS api info
 pod/perlxstut.pod	XS tutorial
diff --git a/lib/byte.pm b/lib/byte.pm
index cc23b40f4f..33ffb769e8 100644
--- a/lib/byte.pm
+++ b/lib/byte.pm
@@ -20,7 +20,7 @@ __END__
 
 =head1 NAME
 
-byte - Perl pragma to turn force treating strings as bytes not UNICODE
+byte - Perl pragma to force byte semantics rather than character semantics
 
 =head1 SYNOPSIS
 
@@ -29,5 +29,24 @@ byte - Perl pragma to turn force treating strings as bytes not UNICODE
 
 =head1 DESCRIPTION
 
+WARNING: The implementation of Unicode support in Perl is incomplete.
+Expect sudden and unannounced changes!
+
+The C<use byte> pragma disables character semantics for the rest of the
+lexical scope in which it appears.  C<no byte> can be used to reverse
+the effect of C<use byte> within the current lexical scope.
+
+Perl normally assumes character semantics in the presence of
+character data (i.e. data that has come from a source that has
+been marked as being of a particular character encoding) or when
+the global $^U flag is enabled.  [XXX: implement -C command line
+switch and mention that instead of $^U?]
+
+To understand the implications and differences between character
+semantics and byte semantics, see L<perlunicode>.
+
+=head1 SEE ALSO
+
+L<perlunicode>, L<utf8>
 
 =cut
diff --git a/lib/byte_heavy.pl b/lib/byte_heavy.pl
index 07c908a689..ec0558561d 100644
--- a/lib/byte_heavy.pl
+++ b/lib/byte_heavy.pl
@@ -1,8 +1,8 @@
 package byte;
 
-sub length ($)
-{
- return CORE::length($_[0]);
+sub length ($) {
+    BEGIN { byte::import() }
+    return CORE::length($_[0]);
 }
 
 1;
diff --git a/lib/utf8.pm b/lib/utf8.pm
index 691de0d630..be7cc0bf0c 100644
--- a/lib/utf8.pm
+++ b/lib/utf8.pm
@@ -1,14 +1,15 @@
 package utf8;
 
-$^U = 1;
+$^U = 1 if caller and caller eq 'main';	# they are unicode aware
+					# XXX split this out?
 
 sub import {
-    $^H |= 0x00000008;
+    $^H |= 0x00800000;
     $enc{caller()} = $_[1] if $_[1];
 }
 
 sub unimport {
-    $^H &= ~0x00000008;
+    $^H &= ~0x00800000;
 }
 
 sub AUTOLOAD {
@@ -21,7 +22,7 @@ __END__
 
 =head1 NAME
 
-utf8 - Perl pragma to turn on UTF-8 and Unicode support
+utf8 - Perl pragma to enable/disable UTF-8 in source code
 
 =head1 SYNOPSIS
 
@@ -30,154 +31,60 @@ utf8 - Perl pragma to turn on UTF-8 and Unicode support
 
 =head1 DESCRIPTION
 
-The utf8 pragma tells Perl to use UTF-8 as its internal string
-representation for the rest of the enclosing block.  (The "no utf8"
-pragma tells Perl to switch back to ordinary byte-oriented processing
-for the rest of the enclosing block.)  Under utf8, many operations that
-formerly operated on bytes change to operating on characters.  For
-ASCII data this makes no difference, because UTF-8 stores ASCII in
-single bytes, but for any character greater than C<chr(127)>, the
-character is stored in a sequence of two or more bytes, all of which
-have the high bit set.  But by and large, the user need not worry about
-this, because the utf8 pragma hides it from the user.  A character
-under utf8 is logically just a number ranging from 0 to 2**32 or so.
-Larger characters encode to longer sequences of bytes, but again, this
-is hidden.
+WARNING: The implementation of Unicode support in Perl is incomplete.
+Expect sudden and unannounced changes!
 
-Use of the utf8 pragma has the following effects:
+The C<use utf8> pragma tells the Perl parser to allow UTF-8 in the
+program text in the current lexical scope.  The C<no utf8> pragma
+tells Perl to switch back to treating the source text as literal
+bytes in the current lexical scope.
 
-=over 4
+This pragma is primarily a compatibility device.  Perl versions
+earlier than 5.6 allowed arbitrary bytes in source code, whereas
+in future we would like to standardize on the UTF-8 encoding for
+source text.  Until UTF-8 becomes the default format for source
+text, this pragma should be used to recognize UTF-8 in the source.
+When UTF-8 becomes the standard source format, this pragma will
+effectively become a no-op.
 
-=item *
-
-Strings and patterns may contain characters that have an ordinal value
-larger than 255.  Presuming you use a Unicode editor to edit your
-program, these will typically occur directly within the literal strings
-as UTF-8 characters, but you can also specify a particular character
-with an extension of the C<\x> notation.  UTF-8 characters are
-specified by putting the hexadecimal code within curlies after the
-C<\x>.  For instance, a Unicode smiley face is C<\x{263A}>.  A
-character in the Latin-1 range (128..255) should be written C<\x{ab}>
-rather than C<\xab>, since the former will turn into a two-byte UTF-8
-code, while the latter will continue to be interpreted as generating a
-8-bit byte rather than a character.  In fact, if C<-w> is turned on, it will
-produce a warning that you might be generating invalid UTF-8.
-
-=item *
+Enabling the C<utf8> pragma has the following effects:
 
-Identifiers within the Perl script may contain Unicode alphanumeric
-characters, including ideographs.  (You are currently on your own when
-it comes to using the canonical forms of characters--Perl doesn't (yet)
-attempt to canonicalize variable names for you.)
+=over
 
 =item *
 
-Regular expressions match characters instead of bytes.  For instance,
-"." matches a character instead of a byte.  (However, the C<\C> pattern
-is provided to force a match a single byte ("C<char>" in C, hence
-C<\C>).)
+Bytes in the source text that have their high-bit set will be treated
+as being part of a literal UTF-8 character.  This includes most literals
+such as identifiers, string constants, constant regular expression patterns
+and package names.
 
 =item *
 
-Character classes in regular expressions match characters instead of
-bytes, and match against the character properties specified in the
-Unicode properties database.  So C<\w> can be used to match an ideograph,
-for instance.
+As a side effect, when this pragma is used within the main package,
+it also enables Unicode character semantics for the entire program.
+See L<perlunicode> for more on that.
 
-=item *
-
-Named Unicode properties and block ranges make be used as character
-classes via the new C<\p{}> (matches property) and C<\P{}> (doesn't
-match property) constructs.  For instance, C<\p{Lu}> matches any
-character with the Unicode uppercase property, while C<\p{M}> matches
-any mark character.  Single letter properties may omit the brackets, so
-that can be written C<\pM> also.  Many predefined character classes are
-available, such as C<\p{IsMirrored}> and  C<\p{InTibetan}>.
+[XXX: split this out into separate "pragma" and/or -C command-line
+switch?]
 
 =item *
 
-The special pattern C<\X> match matches any extended Unicode sequence
-(a "combining character sequence" in Standardese), where the first
-character is a base character and subsequent characters are mark
-characters that apply to the base character.  It is equivalent to
-C<(?:\PM\pM*)>.
-
-=item *
+In the absence of inputs marked as UTF-8, regular expressions within the
+scope of this pragma will default to using character semantics instead
+of byte semantics.
 
-The C<tr///> operator translates characters instead of bytes.  It can also
-be forced to translate between 8-bit codes and UTF-8 regardless of the
-surrounding utf8 state.  For instance, if you know your input in Latin-1,
-you can say:
-
-    use utf8;
-    while (<>) {
-	tr/\0-\xff//CU;		# latin1 char to utf8
-	...
+    @bytes_or_chars = split //, $data;	# may split to bytes if data
+					# $data isn't UTF-8
+    {
+	use utf8;			# force char semantics
+	@chars = split //, $data;	# splits characters
     }
 
-Similarly you could translate your output with
-
-    tr/\0-\x{ff}//UC;		# utf8 to latin1 char
-
-No, C<s///> doesn't take /U or /C (yet?).
-
-=item *
-
-Case translation operators use the Unicode case translation tables.
-Note that C<uc()> translates to uppercase, while C<ucfirst> translates
-to titlecase (for languages that make the distinction).  Naturally
-the corresponding backslash sequences have the same semantics.
-
-=item *
-
-Most operators that deal with positions or lengths in the string will
-automatically switch to using character positions, including C<chop()>,
-C<substr()>, C<pos()>, C<index()>, C<rindex()>, C<sprintf()>,
-C<write()>, and C<length()>.  Operators that specifically don't switch
-include C<vec()>, C<pack()>, and C<unpack()>.  Operators that really
-don't care include C<chomp()>, as well as any other operator that
-treats a string as a bucket of bits, such as C<sort()>, and the
-operators dealing with filenames.
-
-=item *
-
-The C<pack()>/C<unpack()> letters "C<c>" and "C<C>" do I<not> change,
-since they're often used for byte-oriented formats.  (Again, think
-"C<char>" in the C language.)  However, there is a new "C<U>" specifier
-that will convert between UTF-8 characters and integers.  (It works
-outside of the utf8 pragma too.)
-
-=item *
-
-The C<chr()> and C<ord()> functions work on characters.  This is like
-C<pack("U")> and C<unpack("U")>, not like C<pack("C")> and
-C<unpack("C")>.  In fact, the latter are how you now emulate
-byte-oriented C<chr()> and C<ord()> under utf8.
-
-=item *
-
-And finally, C<scalar reverse()> reverses by character rather than by byte.
-
-=back
-
-=head1 CAVEATS
-
-As of yet, there is no method for automatically coercing input and
-output to some encoding other than UTF-8.  This is planned in the near
-future, however.
+[XXX: Should this should be enabled like chr()/sprintf("%c") by looking
+at $^U instead?]
 
-In any event, you'll need to keep track of whether interfaces to other
-modules expect UTF-8 data or something else.  The utf8 pragma does not
-magically mark strings for you in order to remember their encoding, nor
-will any automatic coercion happen (other than that eventually planned
-for I/O).  If you want such automatic coercion, you can build yourself
-a set of pretty object-oriented modules.  Expect it to run considerably
-slower than than this low-level support.
+=head1 SEE ALSO
 
-Use of locales with utf8 may lead to odd results.  Currently there is
-some attempt to apply 8-bit locale info to characters in the range
-0..255, but this is demonstrably incorrect for locales that use
-characters above that range (when mapped into Unicode).  It will also
-tend to run slower.  Avoidance of locales is strongly encouraged.
+L<perlunicode>, L<byte>
 
 =cut
diff --git a/op.c b/op.c
index 6bb7876683..953ee1c42c 100644
--- a/op.c
+++ b/op.c
@@ -2867,7 +2867,7 @@ Perl_pmruntime(pTHX_ OP *o, OP *expr, OP *repl)
 	    p = SvPV(pat, plen);
 	    pm->op_pmflags |= PMf_SKIPWHITE;
 	}
-	else if (DO_UTF8(pat))
+	if ((PL_hints & HINT_UTF8) || (SvUTF8(pat) && !(PL_hints & HINT_BYTE)))
 	    pm->op_pmdynflags |= PMdf_UTF8;
 	pm->op_pmregexp = CALLREGCOMP(aTHX_ p, p + plen, pm);
 	if (strEQ("\\s+", pm->op_pmregexp->precomp))
@@ -2875,6 +2875,8 @@ Perl_pmruntime(pTHX_ OP *o, OP *expr, OP *repl)
 	op_free(expr);
     }
     else {
+	if (PL_hints & HINT_UTF8)
+	    pm->op_pmdynflags |= PMdf_UTF8;
 	if (pm->op_pmflags & PMf_KEEP || !(PL_hints & HINT_RE_EVAL))
 	    expr = newUNOP((!(PL_hints & HINT_RE_EVAL) 
 			    ? OP_REGCRESET
@@ -3401,7 +3403,7 @@ Perl_newSTATEOP(pTHX_ I32 flags, char *label, OP *o)
 	cop->op_ppaddr = PL_ppaddr[ OP_NEXTSTATE ];
     }
     cop->op_flags = flags;
-    cop->op_private = (PL_hints & (HINT_UTF8|HINT_BYTE));
+    cop->op_private = (PL_hints & HINT_BYTE);
 #ifdef NATIVE_HINTS
     cop->op_private |= NATIVE_HINTS;
 #endif
diff --git a/perl.h b/perl.h
index 518f4b3c5a..d89f3a810d 100644
--- a/perl.h
+++ b/perl.h
@@ -2467,8 +2467,8 @@ enum {		/* pass one of these to get_vtbl */
 #define HINT_INTEGER		0x00000001
 #define HINT_STRICT_REFS	0x00000002
 /* #define HINT_notused4	0x00000004 */
-#define HINT_UTF8		0x00000008
-#define HINT_BYTE		0x00000010
+#define HINT_BYTE		0x00000008
+/* #define HINT_notused10	0x00000010 */
 				/* Note: 20,40,80 used for NATIVE_HINTS */
 
 #define HINT_BLOCK_SCOPE	0x00000100
@@ -2487,6 +2487,7 @@ enum {		/* pass one of these to get_vtbl */
 #define HINT_RE_EVAL		0x00200000
 
 #define HINT_FILETEST_ACCESS	0x00400000
+#define HINT_UTF8		0x00800000
 
 /* Various states of an input record separator SV (rs, nrs) */
 #define RsSNARF(sv)   (! SvOK(sv))
diff --git a/pod/perldelta.pod b/pod/perldelta.pod
index cba167f652..2b5e4e7233 100644
--- a/pod/perldelta.pod
+++ b/pod/perldelta.pod
@@ -378,8 +378,9 @@ building and installing from source, the defaults should be fine.
 =head2 Unicode and UTF-8 support
 
 Perl can optionally use UTF-8 as its internal representation for character
-strings.  The C<utf8> pragma enables this support in the current lexical
-scope.  See L<utf8> for more information.
+strings.  The C<utf8> and C<byte> pragmas are used to control this support
+in the current lexical scope.  See L<perlunicode>, L<utf8> and L<byte> for
+more information.
 
 =head2 Interpreter cloning, threads, and concurrency
 
@@ -1653,6 +1654,10 @@ A tutorial that introduces the essentials of references.
 
 A tutorial on managing class data for object modules.
 
+=item perlunicode.pod
+
+An introduction to Unicode support features in Perl.
+
 =back
 
 =head1 New or Changed Diagnostics
diff --git a/pod/perlunicode.pod b/pod/perlunicode.pod
new file mode 100644
index 0000000000..b0efcca8df
--- /dev/null
+++ b/pod/perlunicode.pod
@@ -0,0 +1,202 @@
+=head1 NAME
+
+perlunicode - Unicode support in Perl
+
+=head1 DESCRIPTION
+
+WARNING: The implementation of Unicode support in Perl is incomplete.
+Expect sudden and unannounced changes!
+
+Beginning with version 5.6, Perl uses logically wide characters to
+represent strings internally.  This internal representation of strings
+uses the UTF-8 encoding.
+
+In future, Perl-level operations will expect to work with characters
+rather than bytes, in general.
+
+However, Perl v5.6 aims to provide a safe migration path from byte
+semantics to character semantics for programs.  To preserve compatibility
+with earlier versions of Perl which allowed byte semantics in Perl
+operations (owing to the fact that the internal representation for
+characters was in bytes) byte semantics will continue to be in effect
+until a the C<utf8> pragma is used in the C<main> package, or the C<$^U>
+global flag is explicitly set.
+
+Under character semantics, many operations that formerly operated on
+bytes change to operating on characters.  For ASCII data this makes
+no difference, because UTF-8 stores ASCII in single bytes, but for
+any character greater than C<chr(127)>, the character is stored in
+a sequence of two or more bytes, all of which have the high bit set.
+But by and large, the user need not worry about this, because Perl
+hides it from the user.  A character in Perl is logically just a number
+ranging from 0 to 2**32 or so.  Larger characters encode to longer
+sequences of bytes internally, but again, this is just an internal
+detail which is hidden at the Perl level.
+
+The C<byte> pragma can be used to force byte semantics in a particular
+lexical scope.  See L<byte>.
+
+The C<utf8> pragma is a compatibility device to enables recognition
+of UTF-8 in literals encountered by the parser.  It is also used
+for enabling some experimental Unicode support features.  Note that
+this pragma is only required until a future version of Perl in which
+character semantics will become the default.  This pragma may then
+become a no-op.  See L<utf8>.
+
+Character semantics have the following effects:
+
+=over 4
+
+=item *
+
+Strings and patterns may contain characters that have an ordinal value
+larger than 255.  In Perl v5.6, this is only enabled if the lexical
+scope has a C<use utf8> declaration (due to compatibility needs) but
+future versions may enable this by default.
+
+Presuming you use a Unicode editor to edit your program, such characters
+will typically occur directly within the literal strings as UTF-8
+characters, but you can also specify a particular character with an
+extension of the C<\x> notation.  UTF-8 characters are specified by
+putting the hexadecimal code within curlies after the C<\x>.  For instance,
+a Unicode smiley face is C<\x{263A}>.  A character in the Latin-1 range
+(128..255) should be written C<\x{ab}> rather than C<\xab>, since the
+former will turn into a two-byte UTF-8 code, while the latter will
+continue to be interpreted as generating a 8-bit byte rather than a
+character.  In fact, if C<-w> is turned on, it will produce a warning
+that you might be generating invalid UTF-8.
+
+=item *
+
+Identifiers within the Perl script may contain Unicode alphanumeric
+characters, including ideographs.  (You are currently on your own when
+it comes to using the canonical forms of characters--Perl doesn't (yet)
+attempt to canonicalize variable names for you.)
+
+This also needs C<use utf8> currently.  [XXX: Why?  High-bit chars were
+syntax errors when they occurred within identifiers in previous versions,
+so this should be enabled by default.]
+
+=item *
+
+Regular expressions match characters instead of bytes.  For instance,
+"." matches a character instead of a byte.  (However, the C<\C> pattern
+is provided to force a match a single byte ("C<char>" in C, hence
+C<\C>).)
+
+Unicode support in regular expressions needs C<use utf8> currently.
+[XXX: Because the SWASH routines need to be loaded.  And the RE engine
+appears to need an overhaul to Unicode by default anyway.]
+
+=item *
+
+Character classes in regular expressions match characters instead of
+bytes, and match against the character properties specified in the
+Unicode properties database.  So C<\w> can be used to match an ideograph,
+for instance.
+
+C<use utf8> is needed to enable this.  See above.
+
+=item *
+
+Named Unicode properties and block ranges make be used as character
+classes via the new C<\p{}> (matches property) and C<\P{}> (doesn't
+match property) constructs.  For instance, C<\p{Lu}> matches any
+character with the Unicode uppercase property, while C<\p{M}> matches
+any mark character.  Single letter properties may omit the brackets, so
+that can be written C<\pM> also.  Many predefined character classes are
+available, such as C<\p{IsMirrored}> and  C<\p{InTibetan}>.
+
+C<use utf8> is needed to enable this.  See above.
+
+=item *
+
+The special pattern C<\X> match matches any extended Unicode sequence
+(a "combining character sequence" in Standardese), where the first
+character is a base character and subsequent characters are mark
+characters that apply to the base character.  It is equivalent to
+C<(?:\PM\pM*)>.
+
+C<use utf8> is needed to enable this.  See above.
+
+=item *
+
+The C<tr///> operator translates characters instead of bytes.  It can also
+be forced to translate between 8-bit codes and UTF-8 regardless of the
+surrounding utf8 state.  For instance, if you know your input in Latin-1,
+you can say:
+
+    use utf8;
+    while (<>) {
+	tr/\0-\xff//CU;		# latin1 char to utf8
+	...
+    }
+
+Similarly you could translate your output with
+
+    tr/\0-\x{ff}//UC;		# utf8 to latin1 char
+
+No, C<s///> doesn't take /U or /C (yet?).
+
+C<use utf8> is needed to enable this.  See above.
+
+=item *
+
+Case translation operators use the Unicode case translation tables
+when provided character input.  Note that C<uc()> translates to
+uppercase, while C<ucfirst> translates to titlecase (for languages
+that make the distinction).  Naturally the corresponding backslash
+sequences have the same semantics.
+
+=item *
+
+Most operators that deal with positions or lengths in the string will
+automatically switch to using character positions, including C<chop()>,
+C<substr()>, C<pos()>, C<index()>, C<rindex()>, C<sprintf()>,
+C<write()>, and C<length()>.  Operators that specifically don't switch
+include C<vec()>, C<pack()>, and C<unpack()>.  Operators that really
+don't care include C<chomp()>, as well as any other operator that
+treats a string as a bucket of bits, such as C<sort()>, and the
+operators dealing with filenames.
+
+=item *
+
+The C<pack()>/C<unpack()> letters "C<c>" and "C<C>" do I<not> change,
+since they're often used for byte-oriented formats.  (Again, think
+"C<char>" in the C language.)  However, there is a new "C<U>" specifier
+that will convert between UTF-8 characters and integers.  (It works
+outside of the utf8 pragma too.)
+
+=item *
+
+The C<chr()> and C<ord()> functions work on characters.  This is like
+C<pack("U")> and C<unpack("U")>, not like C<pack("C")> and
+C<unpack("C")>.  In fact, the latter are how you now emulate
+byte-oriented C<chr()> and C<ord()> under utf8.
+
+=item *
+
+And finally, C<scalar reverse()> reverses by character rather than by byte.
+
+=back
+
+=head1 CAVEATS
+
+As of yet, there is no method for automatically coercing input and
+output to some encoding other than UTF-8.  This is planned in the near
+future, however.
+
+Whether a piece of data will be treated as "characters" or "bytes"
+by internal operations cannot be divined at the current time.
+
+Use of locales with utf8 may lead to odd results.  Currently there is
+some attempt to apply 8-bit locale info to characters in the range
+0..255, but this is demonstrably incorrect for locales that use
+characters above that range (when mapped into Unicode).  It will also
+tend to run slower.  Avoidance of locales is strongly encouraged.
+
+=head1 SEE ALSO
+
+L<byte>, L<utf8>, L<perlvar/"$^U">
+
+=cut
diff --git a/pp_ctl.c b/pp_ctl.c
index fd725a347c..716be5eb12 100644
--- a/pp_ctl.c
+++ b/pp_ctl.c
@@ -116,8 +116,6 @@ PP(pp_regcomp)
 	    pm->op_pmflags = pm->op_pmpermflags;	/* reset case sensitivity */
 	    if (DO_UTF8(tmpstr))
 		pm->op_pmdynflags |= PMdf_UTF8;
-	    else
-		pm->op_pmdynflags &= ~PMdf_UTF8;
 	    pm->op_pmregexp = CALLREGCOMP(aTHX_ t, t + len, pm);
 	    PL_reginterp_cnt = 0;		/* XXXX Be extra paranoid - needed
 					   inside tie/overload accessors.  */
diff --git a/regcomp.c b/regcomp.c
index 5972724410..bf08761d43 100644
--- a/regcomp.c
+++ b/regcomp.c
@@ -1339,9 +1339,8 @@ Perl_pregcomp(pTHX_ char *exp, char *xend, PMOP *pm)
     if (exp == NULL)
 	FAIL("NULL regexp argument");
 
-    if (PL_curcop == &PL_compiling ? (PL_hints & HINT_UTF8) : IN_UTF8) {
+    if (pm->op_pmdynflags & PMdf_UTF8) {
 	PL_reg_flags |= RF_utf8;
-	pm->op_pmdynflags |= PMdf_UTF8;
     }
     else
 	PL_reg_flags = 0;
diff --git a/regexec.c b/regexec.c
index acdbd890ae..106c5d1d76 100644
--- a/regexec.c
+++ b/regexec.c
@@ -2335,6 +2335,7 @@ S_regmatch(pTHX_ regnode *prog)
 			I32 onpar = PL_regnpar;
 
 			pm.op_pmflags = 0;
+			pm.op_pmdynflags = (UTF||DO_UTF8(ret) ? PMdf_UTF8 : 0);
 			re = CALLREGCOMP(aTHX_ t, t + len, &pm);
 			if (!(SvFLAGS(ret) 
 			      & (SVs_TEMP | SVs_PADTMP | SVf_READONLY)))
diff --git a/utf8.h b/utf8.h
index 578abc7783..96ae621334 100644
--- a/utf8.h
+++ b/utf8.h
@@ -26,7 +26,7 @@ EXTCONST unsigned char PL_utf8skip[];
 
 END_EXTERN_C
 
-#define IN_UTF8 (PL_curcop->op_private & HINT_UTF8)
+/*#define IN_UTF8 (PL_curcop->op_private & HINT_UTF8)*/
 #define IN_BYTE (PL_curcop->op_private & HINT_BYTE)
 #define DO_UTF8(sv) (SvUTF8(sv) && !IN_BYTE)