require EXPR only accepts Class/Name.pm style module names, not Class::Name.
How frustrating! For that, we provide load_class 'Class::Name'.
It's often useful to test whether a module can be loaded, instead of throwing
an error when it's not available. For that, we provide try_load_class
Finally, sometimes we need to know whether a particular class has been loaded.
Asking %INC is an option, but that will miss inner packages and any class for
which the filename does not correspond to the package name. For that,
we provide is_class_loaded 'Class::Name'.