my %handles;
sub handle_for_name {
    my $f = shift;
    if ($handles{$f}){
        return $handles{$f};
    } else {
        open my $h, '<', $f or die "Can't open file '$f': $!";
       $hanldes{$f} = $h;
       return $h;
    }
}

##</code><code>##

use Memoize;
memoize("handle_for_name");
sub handle_for_name {
    my $f = shift;
    open my $h, '<', $f or die "Can't open file '$f': $!";
    return $h;
}