note bart It doesn't work. Well, it <em>does</em> work, but only if the XFORM routine returns <em>a string of the same length</em> for every item. Otherwise, the sorting could turn out wrong. <P>I've made a very contrived example, containing lots of null bytes, but actually, if you have a sufficiently large amount of array items, you can get the same effect on other bytes as well. <P>Let me demonstrate the effect by sorting a number of variable length strings as is, and with the packed index appended. As is shown, the sorted results are not in the same order at all. <code> use Data::Dumper; $Data::Dumper::Useqq = 1; my @data = map "\0" x $_, 0 .. 5; print Dumper [ sort @data ], [ sort map pack("a*N", $data[$_], $_), 0 .. $#data ]; </code> Result: <code> $VAR1 = [ "", "\0", "\0\0", "\0\0\0", "\0\0\0\0", "\0\0\0\0\0" ]; $VAR2 = [ "\0\0\0\0", "\0\0\0\0\0\0\0\0\5", "\0\0\0\0\0\0\0\4", "\0\0\0\0\0\0\3", "\0\0\0\0\0\2", "\0\0\0\0\1" ]; </code> 287149 287149