heredoc after "" in s/// in eval

This works fine:

eval ' s//<<END.""/e; print
Just another Perl hacker,
END
'or die $@
__END__
Just another Perl hacker,

But this doesn’t:

eval ' s//"$1".<<END/e; print
Just another Perl hacker,
END
'or die $@
__END__
Can't find string terminator "END" anywhere before EOF at (eval 1) line 1.

It fails because PL_sublex_info.super_buf*, added by commit
0244c3a403, are not localised, so, after the "", s/// sees its own
buffer pointers in those variables, instead of its parent string eval.

This used to happen only with s///e inside s///e, but that was because
here-docs would peek inside the parent linestr buffer only inside
s///e, and not other quote-like operators.  That was fixed in
recent commits.

Simply moving the assignment of super_buf* into sublex_push does solve
the bug for a simple "", as "" does sublex_start, but not sublex_push.
We do need to localise those variables for "${\''}", however.

1 files changed, 8 insertions, 1 deletions

diff --git a/t/base/lex.t b/t/base/lex.t
index ce16ef122e..d55b189bfa 100644
--- a/t/base/lex.t
+++ b/t/base/lex.t
@@ -1,6 +1,6 @@
 #!./perl
 
-print "1..57\n";
+print "1..58\n";
 
 $x = 'x';
 
@@ -273,3 +273,10 @@ $test++;
 @a = (1,2,3);
 print "not " unless($a[~~2] == 3);
 print "ok 57\n";
+
+$_ = "";
+eval 's/(?:)/"${\q||}".<<\END/e;
+ok 58 - heredoc after "" in s/// in eval
+END
+';
+print $_ || "not ok 58\n";