smsg: parse_references: micro-optimization

With Perl 5.10+, we can rely on the defined-or-assignment (//=)
operator to avoid repeatedly rewriting an SV.

This may not provide a measurable difference here, but
it's more consistent with current style where things like
commit a05445fb400108e60ede7d377cf3b26a0392eb24
("config: config_fh_parse: micro-optimize") provide a measurable
improvement.

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/PublicInbox/Smsg.pm b/lib/PublicInbox/Smsg.pm
index 2b72e8b5..b4cc2ecb 100644
--- a/lib/PublicInbox/Smsg.pm
+++ b/lib/PublicInbox/Smsg.pm
@@ -83,7 +83,7 @@ sub parse_references ($$$) {
                         warn "References: <$ref> too long, ignoring\n";
                         next;
                 }
-                push(@keep, $ref) unless $seen{$ref}++;
+                $seen{$ref} //= push(@keep, $ref);
         }
         $smsg->{references} = '<'.join('> <', @keep).'>' if @keep;
         \@keep;