Perhaps try it with a hash, like this: (untested)

sub f
{
    my %numbers ;
    foreach ( $q->param )
    {
        /^([0-9]+)/ && $numbers{$1}++ ;
    }
    return keys %numbers;
}
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_______________
DamnDirtyApe

Those who know that they are profound strive for clarity. Those who
would like to seem profound to the crowd strive for obscurity.
            --Friedrich Nietzsche