Read up on File::Find -- it will probably be the most portable and bug-free way to go; and, it just might be the most efficient to code (depending).

If your issue is that you only want to find the first file and then stop, try using

foreach (@files) {
  next unless ($_ eq $img_name); ## skip ones we don't want
  print "$_\n";
  last;
}
## or, if you want all files up to (and including) that name:
foreach (@file) {
  print "$_\n";
  last if ($_ eq $img_name);
}
[download]

I suggest (re-)reading the "Control Structures" part of the Camel book for more.