After looking at the docs again the 'a's should be 'A's. 
a   A string with arbitrary binary data, will be null padded.
A   A text (ASCII) string, will be space padded.

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See also: perlpacktut in the docs.
Update: Added reference to tutorial.

In reply to Re: A more elegant use of unpack by wfsp
in thread A more elegant use of unpack by maida

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