Then you have a broken Perl. 

$ perl -e'use warnings; my %keys={A=>"b"};'
Reference found where even-sized list expected at -e line 1.

$ perl -v

This is perl, v5.10.0 built for i686-linux

Copyr...

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I still am fuzzy about the difference between “square brackets,” “braces,” and “parentheses.”

Square brackets create an array and return a reference to the array.
Curly brackets create a hash and return a reference to the hash.
Parens are like in Math. They change the order of operations.

From that, it follows that one never uses [] or {} when initialising an array or hash*, and that parenthesis aren't related to array or hash initialisation.

* — They might be used in initialising the value of an array or hash element's value, though.

Update: I added the last paragraph and the associated "*". I thought it was obvious, especially in the context of the other replies, but it might need saying.

In reply to Re^2: Why? (each...) by ikegami
in thread Why? (each...) by locked_user sundialsvc4

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