++ for asking good questions.

Yes the !@F handles blank lines. When split, these will leave the @F array unpopulated, so scalar(@F) will be 0, or false, and the line gets skipped.

The %h is a Hash of Hashes. the outer "for sort keys %h" handles the first (outer) hash.
Inside that, I use a "hash slice" to get an array of values for keys specified by @w (which is a sorted array).

This is pretty much the same thing kcott does in his line: 

    map { $data{$name}{$_} || '' } @codes;

[download]
except - my code does not worry about non-existing keys - since I run without 'warnings', my code does the right thing without complaint.

        What is the sound of Perl? Is it not the sound of a wall that people have stopped banging their heads against?
              -Larry Wall, 1992

In reply to Re^3: Print something when key does not exist by NetWallah
in thread Print something when key does not exist by jaypal

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