$my $counter = 1;
use Errno qw[ EEXIST ];
sub mk_new_dir {
  while(1){
    my $name = $word . '_' . $counter++;
    if( mkdir $name, 0755 ){
      return $name;  # success, return new dir name
    } else {
      next if $!{EEXIST}; # mkdir failed because the file exists; loop and try next name
      die $!;             # it failed for some other reason; bail out!
    }
  }
}