X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperlre.pod;h=42017ddf6629661a082bb46ab08273ae43864308;hb=93592fd5aeec89ac25994a493ef54e1d7a572d65;hp=58c3dc73e2aa427c3d22fe0ccfdcfa98e20b0291;hpb=8eb5594e5b00118ae265dfff7fa7bd96290d4ed3;p=p5sagit%2Fp5-mst-13.2.git

diff --git a/pod/perlre.pod b/pod/perlre.pod
index 58c3dc7..42017dd 100644
--- a/pod/perlre.pod
+++ b/pod/perlre.pod
@@ -518,6 +518,10 @@ backreference only if at least 11 left parentheses have opened
 before it.  And so on.  \1 through \9 are always interpreted as
 backreferences.
 
+If the bracketing group did not match, the associated backreference won't
+match either. (This can happen if the bracketing group is optional, or
+in a different branch of an alternation.)
+
 X<\g{1}> X<\g{-1}> X<\g{name}> X<relative backreference> X<named backreference>
 In order to provide a safer and easier way to construct patterns using
 backreferences, Perl provides the C<\g{N}> notation (starting with perl
@@ -946,13 +950,6 @@ The assignment to C<$^R> above is properly localized, so the old
 value of C<$^R> is restored if the assertion is backtracked; compare
 L<"Backtracking">.
 
-Due to an unfortunate implementation issue, the Perl code contained in these
-blocks is treated as a compile time closure that can have seemingly bizarre
-consequences when used with lexically scoped variables inside of subroutines
-or loops.  There are various workarounds for this, including simply using
-global variables instead.  If you are using this construct and strange results
-occur then check for the use of lexically scoped variables.
-
 For reasons of security, this construct is forbidden if the regular
 expression involves run-time interpolation of variables, unless the
 perilous C<use re 'eval'> pragma has been used (see L<re>), or the
@@ -974,9 +971,15 @@ so you should only do so if you are also using taint checking.
 Better yet, use the carefully constrained evaluation within a Safe
 compartment.  See L<perlsec> for details about both these mechanisms.
 
-Because Perl's regex engine is currently not re-entrant, interpolated
-code may not invoke the regex engine either directly with C<m//> or C<s///>),
-or indirectly with functions such as C<split>.
+B<WARNING>: Use of lexical (C<my>) variables in these blocks is
+broken. The result is unpredictable and will make perl unstable. The
+workaround is to use global (C<our>) variables.
+
+B<WARNING>: Because Perl's regex engine is currently not re-entrant,
+interpolated code may not invoke the regex engine either directly with
+C<m//> or C<s///>), or indirectly with functions such as
+C<split>. Invoking the regex engine in these blocks will make perl
+unstable.
 
 =item C<(??{ code })>
 X<(??{})>