Without trying to optimize anything, here's an approach using Mail::Address:

# @emails exists already
use Mail::Address;
my @sorted_by_domain_then_user =
    map { $_-> format }
        sort { $a->host cmp $b->host
                or $a->user cmp $b->user }
            map {Mail::Address->parse($_)} @emails;
[download]

This may not be exactly what you want, but should be close.

After Compline,
Zaxo