The following works, though it can definitely be made more efficient by using @_ instead of creating private variables in each instance of the sub, and by returning sets of matches instead of passing a potential set to each successive instance of the sub. Of course, this means you can only view the results once they're all in, instead of while they're being generated. Note that I'm passing the number array by reference rather than individual numbers, which should increase efficiency assuming the array starts out fairly big.

use strict;
use warnings;

my @array = (6, 18, 12, 2, 49);
addup(2, 30, 0, [sort {$b <=> $a} @array]);

sub addup {
    my ($num, $val, $offset, $p, @set) = @_;
    if ($num == 1) {
        for ($offset..$#{$p}) {
            last if @$p[$_] < $val;
            print join ' ', @set, $val, "\n" if @$p[$_] == $val;
        }
    }
    else {
        for ($offset..($#{$p}-$num+1)) {
            next if @$p[$_] > $val - $num + 1;
            last if @$p[$_] < int ($val / $num);
            addup($num-1, $val-@$p[$_], $_+1, $p, @set, @$p[$_]);
        }
    }
}
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