In perl, methods are always called with either a class or an object as its first parameter, usually by writing:

$class_or_object->method(other arguments);
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$class_or_object here can be a real object (an instance of a a class) or a class name (IOW, a string containing the package name designating the class), or a class name as a bare word.

Note the -> arrow. That means that the function is going to be looked up and called as a method. If you call the function directly, as in MyPackage::some_method() the call will not behave as a method but just like a plain function call. In other words; perl distinguishes between methods and functions only by the way they are called.

To answer your question directly: feat->mymethod() should work.

Note that more-or-less officially, all-lowercase module/package names are reserved for pragmas, which are very uncommon outside the base distribution, so while nothing aside from a potential clash with an existing pragma will stop you from using all-lowercase names, it's generally frowned upon. It also makes it harder to spot class names.