The answer is to use anonymous sub. This happens quite often with Tk, if you use it.

$mw->Button(command => \&some_func)->pack();
[download]

What if the func takes parameter(s), or the func is a class method. The answer is still the same, anonymous sub, you can just do:

$mw->Button(command => sub {$obj->some_func($param1, $param2)})->pack(
+);
[download]