...
sub pi () { 4 * CORE::atan2(1, 1) }
...
sub cos {
    my ($z) = @_ ? @_ : $_;
    return CORE::cos($z) unless ref $z;
    ...
}
...
sub sin {
    my ($z) = @_ ? @_ : $_;
    return CORE::sin($z) unless ref $z;
    ...
}
...