But wait! What if we already had $_ defined? Nesting these expressions: dangerous? while (<>) { if (my ($trusted) = /trusted_users = (.*)/x) { foreach (split /,/, $trusted) { $current_user->register_trust($_); } } # some more handling: what happens to $_? } This works well, because $_ was localized by the foreach and restored after it. So we're safe... Implicitly: local $_; foreach $_ (split /,/ $trusted) { # ...