use strict;
use warnings;
use Data::Dump;

my %depends;

while (<DATA>) {
    chomp;
    
    my ($job, @deps) = split ',';
    
    $depends{$job}{$_} = undef for @deps;
}

addDepends (\%depends, $_, keys %{$depends{$_}}) for keys %depends;

print Data::Dump::dump(\%depends);


sub addDepends {
    my ($depends, $target, @deps) = @_;
    
    for my $dep (@deps) {
        next if $depends->{$target}{$dep}++;
        
        addDepends($depends, $target, keys %{$depends{$dep}});
    }
}

__DATA__
job1,
job2,job1,
job3,job2
job4,job2
job5,job2,job4
job6,jobz
joba,job4,jobb
jobz,jobbc,job2