#!/usr/bin/env perl
use strict;
use warnings;

my $user1 = [ [ 'alpha@foo.com', 'beta@foo.dom' ], [ 'gamma@foo.com' ] ];
my $user2 = [ [ 'delta@foo.com' ], [ 'epsilon@foo.dom', 'zeta@foo.com' ] ];

my $TotalEmails = [ @$user1, @$user2 ];

my @to;
for my $em ( @$TotalEmails ) {
    push @to, @$em;
}

my $tostring = join ',', @to;
print "Full list of addrs: $tostring\n";