my @input = qw(0:6
0:12
0:18
0:24
6:12
6:18
6:24
12:18
12:24
18:24);

my %link;
for (@input) {
    my ($key, $value) = split /:/;
    push @{$link{$key}}, $value;
}
##</code><code>##

$VAR1 = {
          '6' => [
                   '12',
                   '18',
                   '24'
                 ],
          '18' => [
                    '24'
                  ],
          '0' => [
                   '6',
                   '12',
                   '18',
                   '24'
                 ],
          '12' => [
                    '18',
                    '24'
                  ]
        };