for my $subdir ( sort @subdirs ) {
   chdir($dir);

   ...

   my $in_fh1;
   if (!open $in_fh1, '<', $infile1) {
      goto NEXT if $!{ENOENT};
      die qq{Failed to open "$infile1" for reading: $!};
   }

   ...

NEXT:
   chdir('..');
}