$pm->run_on_finish(sub {
    my ($pid, $exit_code, $ident) = @_;       
    my ($action, $host) = $ident =~ /^(.*?) on (.*)/s;
    printf "run_on_finish: %s (pid: %s exited with code: %s\n",
        $ident, $pid, $exit_code;
    insert_into_db(\$dbh, $host, $action, $exit_code);      
});

##</code><code>##

for my $host (@hosts) {
    if (!$pm->start("cmd1 on $host")) {
        exec(@cmd1, $host);
        print(STDERR "cmd1 exec failed: $!\n");
        _exit($!); 
    }
    if (!$pm->start("cmd2 on $host")) {
        exec(@cmd2, $host);
        print(STDERR "cmd2 exec failed: $!\n");
        _exit($!); 
    }
}

##</code><code>##

for my $host (@hosts) {
    for (
        [ cmd1 => \@cmd1 ],
        [ cmd2 => \@cmd2 ],
    ) {
        my ($action, $cmd) = @$_;
        $pm->start("$action on $host") and next;
        exec(@$cmd, $host);
        print(STDERR "$action exec failed: $!\n");
        _exit($!); 
    }
}