no, at all, if you look carefully at what he posted you'll find this:

%hash = {no_arg => \&print_me,
        with_arg => \&print_me("Hello World, again!\n"
        };
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as you can see he uses curly brackets to build a hash and lacks right parenthesis just after "Hello World, again!\n"
what i say is that this code will never work (maybe is just a wrong trascription) and that you can't do

bar  =>\&do_bar("argument")
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so you have to do

bar => sub { do_bar("argument") }
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that's all..
update of course (foo => \&foo) with no arguments is perfectly legal..