sub trim {
    if ( !@_ && !defined(wantarray) ) { carp 'Useless use of trim with no arguments in void return context (did you mean "trim($_)"?)'; return; }
    if ( !@_ ) { carp "Useless use of trim with no arguments"; return; }
    @_ = @_ if defined wantarray;

    for (@_) { s/\A\s+//; s/\s+\z// }

    return wantarray ? @_ : "@_";
}