Just for fun/whatever insight it might bring, here's a recursive, no-modules solution that generates only the matching combinations.

use warnings;
use strict;

# A mech is an arrayref of three attributes: name, weight, 'clan'
my @mechs = map [split], <DATA>;

# find all lances with M members and <=W weight
my @possible_lances = find_lances (3, 150, @mechs);
print 'Found '.@possible_lances, " sets\n";
print join(',', map($_->[0], @$_)), "\n" for @possible_lances;


# Return an array of arrayrefs. Each arrayref contains a set (lance) o
+f mechs.
sub find_lances
{
    my ($M, $W, $first, @rest) = @_;
    # If there aren't enough mechs left, or you're overweight, no matc
+h
    if ($M < 1 or $M-1 > @rest or $W < 0) { return () }
    # Base case
    elsif ($M == 1) {
        return(map [$_], grep { $_->[1] <= $W } $first, @rest);
    }
    else {
        return (
                # All qualifying sets that include the 1st element
                do {
                    if ($first->[1] <= $W) {
                        map [$first, @$_], 
                          find_lances($M-1, $W-$first->[1], @rest);
                    }
                    else { () }
                },
                # and all qualifying sets that do not include the 1st 
+element
                find_lances($M, $W, @rest)
               );
    }
}

__DATA__
Flea 20 clan
Commando 25 clan
UrbanMech 30 clan
Hollander 35 clan
Jenner 35 clan
Raven 35 clan
Wolfhound 35 clan
BlackHawk 50 clan
Hunchback 50 clan
Rifleman 60 clan
Catapult 65 clan
Loki 65 clan
Thor 70 clan
MadCat 75  clan
Gargoyle 80 clan
Victor 80 clan
Zeus 80 clan
Longbow 85 clan
Warhawk 85 clan
Mauler 90 clan
Atlas 100 clan
[download]