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

package Foo;
use Readonly;
Readonly my  $C1 => 'const1';
Readonly our $C2 => 'const2';
sub get_c1 { return $C1 }
1;

perl -MFoo -e 'print "$_\n" for Foo->get_c1, $Foo::C2'