How pre-5.9.0 Perl can be fooled by a defined-or.

p4raw-id: //depot/perl@18091

1 files changed, 5 insertions, 0 deletions

diff --git a/pod/perldiag.pod b/pod/perldiag.pod
index e1c9a069ab..4f9112bea0 100644
--- a/pod/perldiag.pod
+++ b/pod/perldiag.pod
@@ -3239,6 +3239,11 @@ or setgid bit set.  This doesn't make much sense.
 construct.  Remember that bracketing delimiters count nesting level.
 Missing the leading C<$> from a variable C<$m> may cause this error.
 
+Note that since Perlf 5.9.0 a // can also be the I<defined-or>
+construct, not just the empty search pattern.  Therefore code written
+in Perl 5.9.0 or later that uses the // as the I<defined-or> can be
+misparsed by pre-5.9.0 Perls as a non-terminated search pattern.
+
 =item %sseek() on unopened filehandle
 
 (W unopened) You tried to use the seek() or sysseek() function on a