I think you introduced unneeded complexity here.

Off the top of my head:

use File::Find;

my ($search, $ext) = @ARGV;
$ext = ".$ext" if defined $ext;
@ARGV = ();
find sub { push @ARGV, $_ if -f and not $ext or /\Q$ext$/ }, ".";
while (<>) {
  close ARGV if eof;
  print "$ARGV: $. :$_\n" if /$search/;
}
[download]

There's a few optimizations with qr// if you're really into speed, but this should handle 90% of it.

-- Randal L. Schwartz, Perl hacker