Implement the fc keyword and the \F string escape.

Along with the simple_casefolding and full_casefolding features.

fc() stands for foldcase, a sort of pseudo case (like lowercase),
which is used to implement Unicode casefolding. It maps a string
to a form where all case differences are erased, so it's a
locale-independent way of checking if two strings are the same,
regardless of case.

This functionality was, and still is, available through the
regular expression engine -- /i matches would use casefolding
internally. The fc keyword merely exposes this for easier access.

Previously, one could attempt to case-insensitively test two strings
for equality by doing

   lc($a) eq lc($b)

But that might get you wrong results, for example in the case of
\x{DF}, LATIN SMALL LETTER SHARP S.

1 files changed, 1 insertions, 0 deletions

diff --git a/pp_proto.h b/pp_proto.h
index 96bcacbe6b..52011dadd3 100644
--- a/pp_proto.h
+++ b/pp_proto.h
@@ -66,6 +66,7 @@ PERL_CALLCONV OP *Perl_pp_eq(pTHX);
 PERL_CALLCONV OP *Perl_pp_exec(pTHX);
 PERL_CALLCONV OP *Perl_pp_exists(pTHX);
 PERL_CALLCONV OP *Perl_pp_exit(pTHX);
+PERL_CALLCONV OP *Perl_pp_fc(pTHX);
 PERL_CALLCONV OP *Perl_pp_fileno(pTHX);
 PERL_CALLCONV OP *Perl_pp_flip(pTHX);
 PERL_CALLCONV OP *Perl_pp_flock(pTHX);