#! perl -slw
use strict;

sub dedup {
    my $ref = shift;
    my ($r, $l, %h);
    $r=$l=0;
    while( $r < @$ref ) {
        if ($h{$ref->[$r]}++) {
                # already seen
                ++$r;
        }
        else {
                # not yet seen. Copy!
                $ref->[$l++]= $ref->[$r++];
        }
    }