sub remove_duplicates(\@)
{
	my $ar = shift;
	my %seen;
	for ( my $i = 0; $i <= $#{$ar} ; )
	{
		splice @$ar, --$i, 1
			if $seen{$ar->[$i++]}++;
	}
}

my @a = qw( a a b c c c d e f e f e a f g h h h );
remove_duplicates( @a );
print "@a\n";