To expand on ikegami's response, using a Schwartzian Transform only makes sense when the item(s) by which to sort is/are obtained by some expensive transformation. That transformation gets repeated many times for each element being sorted as the sort algorith moves it into the right place by successive comparisons with other elements. There was no transformation required in your code as $hash{$_}{desc} could be accessed directly.

Consider the following two code snippets that sort files by modification time (requiring an lstat call, our expensive transformation). Note the timings; using Benchmark would be better but this was just a quick example.

knoppix@Knoppix:~$ time perl -Mstrict -wle '
-> my $d = q{/usr/bin};
-> my @fns = do { opendir my $dh, $d or die $!; readdir $dh };
-> my @sorted =
->    sort { ( lstat qq{$d/$a} )[ 9 ] <=> ( lstat qq{$d/$b} )[ 9 ] }
->    @fns;'

real    0m1.614s
user    0m0.307s
sys    0m1.273s
knoppix@Knoppix:~$ time perl -Mstrict -wle '
-> my $d = q{/usr/bin};
-> my @fns = do { opendir my $dh, $d or die $!; readdir $dh };
-> my @sorted =
->    map  { $_->[ 0 ] }                                            
->    sort { $a->[ 1 ] <=> $b->[ 1 ] }
->    map  { [ $_, lstat qq{$d/$_} ] }
->    @fns;'

real    0m0.281s
user    0m0.100s
sys    0m0.160s
knoppix@Knoppix:~$

[download]

I hope this is of interest.

Cheers,

JohnGG

In reply to Re^2: Sort of anonymous hash by johngg
in thread Sort of anonymous hash by larsss31

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