Esteemed Monks, I would like to sort a multi-dimensional array (LoL), based on the value of a particular subscript in the second-level array.

Here is some test code: 
#!/usr/bin/perl

my $aref = [[(1..10)],
            [(30..40)],
            [qw(the quick brown fox)],
            [qw(jumps over the lazy dog)]
    ];

for (@$aref) {
    print "$_: @$_\n";
}

print "\n";

# print some values, just to test whether dereferencing is correct
print ${$$aref[0]}[0], "\n";
print $aref->[0]->[0], "\n";
print $aref->[1]->[0], "\n";
print $aref->[2]->[0], "\n";
print $aref->[3]->[0], "\n";

print "\n";

for (sort { $aref->[$a]->[0] cmp $aref->[$b]->[0] } @$aref) {
    print "$_: @$_\n";
}

[download]
This returns: 

ARRAY(0x8153c28): 1 2 3 4 5 6 7 8 9 10
ARRAY(0x8154630): 30 31 32 33 34 35 36 37 38 39 40
ARRAY(0x81548a0): the quick brown fox
ARRAY(0x8154a50): jumps over the lazy dog

1
1
30
the
jumps

Out of memory!

[download]

An easy work-around (that I can think of) would be to use an intermediate hash (turning the structure into a HoL), then sorting on the hash keys. But I would like to understand why the above code does not work.

Thanks!

-lbmp

In reply to Sort multi-dimensional array based on dereferenced value - out of memory error by lbmp

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