When given to pack() it consumes a list of strings and returns a single string where every string is now prefixed with the length, encoded in a big-endian 32 bit value. Its fantastic for serializing a bunch of strings. Do note - I wrote the format backwards so the "N" comes before the "A*". pack will tell you this as well so you can't make the mistake and let it just get away from you.

pack '(N/a*)*', list of strings;

$foo = pack '(N/a*)*', "A", "BB", "CCC", "DDDD";

$foo eq ( "\0\0\0\1A" . "\0\0\0\2BB" . "\0\0\0\3CCC" . "\0\0\0\4DDDD" 
+);
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