sub Widget::Munge {
    # code block A
    if(  $self->is_blue()  ) {
        # code block B
    } else {
        # code block C
    }
    # code block D
}

##</code><code>##

sub Widget::Munge {
    # code block A
    # code block C
    # code block D
}
sub Widget::Blue::Munge {
    # code block A
    # code block B
    # code block D
}