prototypes parens/parenthesis hash initialization/declaration / Too many arguments for / $$

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

I'm confused, I thought this would work

$ perl -MData::Dump -e " sub ff($$){ qq{@_} } my %f = ( 12 => ff 1,2, 
+34 => ff 3,4 ); dd\%f "
Too many arguments for main::ff at -e line 1, near "4 )"
Execution of -e aborted due to compilation errors.
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without having to type parens like

$ perl -MData::Dump -e " sub ff($$){ qq{@_} } my %f = ( 12 => ff( 1,2)
+ , 34 => ff( 3,4) ); dd\%f "
{ 12 => "1 2", 34 => "3 4" }
[download]

A prototype of ($) doesn't require parens ... anyone?

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