module for loading modules by name

 "require EXPR" only accepts Class/Name.pm style module names, not
 Class::Name. For that, Class::Load provides "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, Class::Load provides
 "try_load_class 'Class::Name'".
 .
 Finally, sometimes it is important 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, this module provides "is_class_loaded 'Class::Name'".