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/;
}