#!/usr/bin/perl

sub radix_sort {
    my $array = shift;

    my $from = $array;
    my $to;

    # All lengths expected equal.
    for ( my $i = length $array->[ 0 ] - 1; $i >= 0; $i-- ) {
        # A new sorting bin.
        $to = [ ];
        foreach my $card ( @$from ) {
            # Stability is essential, so we use push().
            push @{ $to->[ ord( substr $card, $i ) ] }, $card;
        }

        # Concatenate the bins.

        $from = [ map { @{ $_ || [ ] } } @$to ];
    }

    # Now copy the elements back into the original array.

    @$array = @$from;
}

@array = qw(flow loop pool Wolf root sort tour);
radix_sort(\@array);
print "@array\n";