#!/usr/bin/perl
use strict;
use warnings;

my %uniq = ();

while (<DATA>) {
    chomp;
    my ($foo, $bar) = split /\*/;
    $uniq{$bar} = $foo;
}

print "$_\n" foreach (keys %uniq);

__DATA__
user1*house
user2*nothing
user3*house
user4*house
user5*other
user6*nothing
user7*main