#! 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++];
        }
    }
##</code><code>##

    $#$ref=$l-1
}
my @a = (7, 20..30, 1..1000, 200..300, 7);

print scalar @a;
dedup \@a;
print scalar @a;
#print "@a";