Dear Monks,

I am struggling to understand the more advanced (un)pack templates, which allow me to describe my data structure.

I have this structure packed in a string $testinput:

byte: number of members in each of the following arrays

array of bytes

array of unsigned shorts

another array of unsigned shorts

I would like to know, if there is a single unpack template, that uses the first entry not only for sizing the following array, but instead three times for each of them.

This is what I have tried so far, and I am not really happy with it.

use strict;
use warnings;

my $testinput = pack('C/a* a* a*', 
                     (pack 'C*', 1, 2), 
                     (pack 'v*', 3, 4),
                     (pack 'v*', 5, 6));

print join(',', unpack('C/C* v2 v2', $testinput)), "\n";
# gives "1,2,3,4,5,6" which is ok,
# but has the repeat factors for 'v' hardcoded

my $repeat = unpack('C', $testinput);
print join(',', unpack("C/C* v$repeat v$repeat", $testinput)), "\n";
# gives "1,2,3,4,5,6" which is ok, but uses two steps
[download]

Is it possible to use one call to unpack to expand this string to the values above?

Thanks in advance, hexcoder

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