Since answers to your question have been given already I just felt like writing the test code without a lot of extra variables, just because I love map: $_->() for map @$_, values %HoL; If you don't want all values, and/or want the subroutines in order, you can do: $_->() for map @$_, @HoL{qw/ one two /}; I don't know if it's more readable, but personally I find it more concise and more straight to the point than nestled for loop with extra and only once used variables.

If you want the return values from the callbacks it gets extra nifty: @ret = map $_->(), map @$_, @HoL{qw/ one two /}; I also want to warn about dereferencing the callback without parentheses, as often seen when using the & to dereference it. It doesn't do what you think, and the issue is covered in perlfaq7, "What's the difference between calling a function as &foo and foo()?".

Looking at the code again though, I noticed that you do (\&hello, \&goodbye,) There's nothing wrong with that, but I figured you'd perhaps be glad to know that you can use the dangerously-looking \(&hello, &goodbye,) instead to save yourself a couple of backslashes. No, the subroutines does not get called. \(...) is quite special. Be sure to check it out in perlref (perlop will just point you there anyway).

Cheers,
ihb

PS. Yes, I love map. :)