I had this older script that was doing something similar, but with two values separated by tab:

use strict;
use warnings;

my %res;
while (<>) 
{
    chomp;
    my ( $name, $rest ) = split /\t/;
    push @{ $res{$name} }, $rest;
}
for ( sort keys %res ) 
{
    print "$_:", join( ",", @{ $res{$_} } );
    print "\n";
}
[download]

but I do not know how to adapt it.