# You never, ever want to call this.
sub perl_unused_by_me
{
    # You have to make sure your scope is correct here.
    $main::variable = 0;
    # You might also consider something like
    # undef $main::variable;
    # so that if this gets called by accident then your
    # code will produce an error at that point, not
    # silently use the bad data.
}