Well, OK.

(Why do I respond to something like this?)

This is your Prolog ported to Perl. Now somebody else can make that shorter ;-) ...

#!/usr/bin/perl -w
use strict;

my $input = [12, 2, 2, 'w', 3, 3, 's', 's', 's'];
my ($head, @tail) = @{$input};

print "@{runcode(\@tail, $head, 1, [])}";

sub runcode {
    my ($tail, $current_head, $count, $output) = @_;
    return [@{$output}, "$count*$current_head"] 
        unless @{$tail};
    my ($head, @tail) = @{$tail};
    if ("$current_head" eq "$head") {
        return runcode(\@tail, $head, ++$count, $output)
    }
    return runcode(\@tail, 
                   $head, 
                   1, 
                   [@{$output}, "$count*$current_head"]);
}
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Christian Lemburg
Brainbench MVP for Perl
http://www.brainbench.com