seek($fh, 2*16, 0); # Double up 'cause 'seek' wants bytes not short ints

Rather than having numeric literals running around all over the place, it's possible to capture pack-spec widths:

c:\@Work\Perl>perl -wMstrict -le
"use constant SIZEOF_S => length pack 'x[S]';
 print SIZEOF_S;
 ;;
 use constant SIZEOF_WHATEVER => length pack 'x[NSc]';
 print SIZEOF_WHATEVER;
"
2
7
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(It may be perfectly safe to use the shorter  'S' etc., rather than the more verbose  'x[S]' form in the pack statement, but I have the sneaking suspicion that a pitfall may lurk there... can't remember it atm.)