How do I use constants from a Perl module?

Question

If I define a constant in a Perl module, how do I use that constant in my main program? (Or how do I call that constant in the main program?)

Answer 1

To add to the bag of tricks, since a constant is just a subroutine you can even call it as a class method.

package Foo;
use constant PI => 3.14;

print Foo->PI;

If you have lots of constants it's a nice way to get at the occasional one without having to export them all. However, unlike Foo::PI or exporting PI, Perl will not compile out Foo->PI so you incur the cost of a method call (which probably doesn't matter).