c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my @lines = (
   'foo: 12 : //comment twelve ',
   'bar: 13 : //comment thirteen',
   'foo:  5  : //comment five',
   );
 ;;
 my %hash;
 for my $line (@lines) {
   my ($k, $v) = split qr{ : \s+ }xms, $line, 2;
   push @{ $hash{$k} }, $v;
   }
 dd \%hash;
"
{
  bar => ["13 : //comment thirteen"],
  foo => ["12 : //comment twelve ", "5  : //comment five"],
}