#! perl -slw
use strict;

sub dedup {
	my $ref = shift;
	my ($i, $count, %h) = (0, 0);
	while( $i < @$ref ) {
		my $v = $ref->[$i];
		unless( exists $h{$v} ) {
			$h{$v}=undef;
			$i++;
			next unless $count;
			$i -= $count;
			splice @{$ref}, $i-1, $count;
			$count = 0;
			next;
		}
		$count++;
		$i++;
	}
	$i -= $count;
	splice @{$ref}, $i, $count;
}
my @a = (5, 1..2, 1..10, 2..5, 7);

print scalar @a, ":@a";
dedup \@a;
print scalar @a, ":@a";