9.5. Multi-Level Sort with the Schwartzian Transform
If we need to sort on more than one criterion, the Schwartzian Transform is still up to the task.
my @output_data =
map $_->[0],
sort { SORT COMPARISON USING $a->[1] AND $b->[1] or
ANOTHER USING $a->[2] AND $b->[2] or
YET ANOTHER USING $a->[3] AND $b->[3] }
map [ $_, SOME FUNCTION OF $_, ANOTHER, YET ANOTHER ],
@input_data;
This code skeleton has a three-level sort comparison, using three computed values saved in the anonymous array (alongside the original data item to be sorted, which always comes first).
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