Hi Monks!

My question is about the following code example, taken as is from Wikipedia:

@sorted = map  { $_->[0] }
          sort { $a->[1] <=> $b->[1] } # use numeric comparison
          map  { [$_, length($_)] }    # calculate the length of the s
+tring
               @unsorted;
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The above is pure Perl, not some generic pseudocode, and what worries me is that length() doesn't seem like a particularly good example for illustrating the concept. It has always been my understanding that in Perl, length($var) just returns whatever value is stored in the corresponding internal SV structure (Devel::Peek calls this field "CUR"; non-string/non-PV scalars don't have this attribute, more on them below). And if it is immediately available, why cache it?

#!/usr/bin/perl

use strict;
use Devel::Peek;

my @arr = (22, 5.555, 1, 4444, 333);

print Dump(\@arr, @arr+0), "\n\n\n";
# at this point, there are 4 IVs and one NV in our array;
# naturally, none of the elements have their length ("CUR") field set

my ($retval, $just_once);

my @sorted = sort {
    # does this alter the internal structures of our actual
    # array elements, turning IVs and NVs into PVIVs/PVNVs?
    $retval = length $a <=> length $b;

    print Dump \@arr, @arr+0 if !$just_once++;
    # of course it does!

    $retval;
} @arr;

print "\nsorted = @sorted\n";
[download]

I might be missing something here, so please correct me if I'm wrong.