Sub calling sadness

[nefigah]

I've seen warnings in the docs/on PM/in books about how to call functions, and it finally bit me in a weird way.

Oddly, I recall someone saying that user-defined functions SHOULDN'T be called using & (and if you do use it, to make sure you use parentheses).

That sounded good to me, so I was avoiding using & and (), when I ran into this sort of scenario (in my unit test file):

use Test::More 'no_plan';
require 'some_file_with_my_functions.pm';

my $foo = "hi";
my $bar = " hi";

ok( ThatPackage::blah $foo, 'blah' );
ok( ThatPackage::blah $bar, 'blah2' );

(Names changed to protect the innocent.)

So I get an error at the blah2 test, (like, not the test failing, but a compile error) and was very confused.

Well, putting parentheses thusly fixed it:
ok( ThatPackage::blah($bar), 'blah2' );

Which is fine and dandy, but makes me somewhat sad because I don't understand why that's necessary just because the stupid string in $bar has leading whitespace. :(

I don't suppose some kind monk could make sense of it for me?

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