sub gmtime {
    my $time = shift;
    $time = time if (!defined $time);
    _mktime($time, 0);
}

sub _mktime {
    my ($time, $islocal) = @_;
    if (ref($time)) {
	$time->[c_epoch] = undef;
	return wantarray ? @$time : bless [@$time, $islocal],
                                          'Time::Piece';
    }
    my @time = $islocal ?
            CORE::localtime($time)
                :
            CORE::gmtime($time);
    wantarray ? @time : bless [@time, $time, $islocal], 'Time::Piece';
}


##</code><code>##

  package Time::MyPiece;
  use base 'Time::Piece';
  my $SUPER;
  foreach (@ISA) {
    $SUPER = $_ and last if $_->can('_mktime');
  }

  ...

  sub _mktime {
    my $t;
    eval "$t = $SUPER::_mktime(@_)";
  }

##</code><code>##

sub _mktime {
    my ($time, $islocal) = @_;
    my $class;
    if (ref $time) {
      $class = ref $time;
    }
    elsif ($time =~ /^\D+$/) {
      $class = $time;
      $time = $class->new(@_);
    }
    if (ref($time)) {
	$time->[c_epoch] = undef;
	return wantarray ? @$time : bless [@$time, $islocal], $class;
    }
    my @time = $islocal ?
            CORE::localtime($time)
                :
            CORE::gmtime($time);
    wantarray ? @time : bless [@time, $time, $islocal], $class;
}