I'm not quite sure I understand your question, but I think I do. I think a hash would be the easiest way to go.

#!/usr/bin/perl -w
use strict;

my (@newa, %hash, @sortedlist, @sortedindex);

@newa = ('t', 'd', 'z', 'x'); 
@hash{@newa}=(0..$#newa);
@sortedlist=sort @newa;
@sortedindex=@hash{@sortedlist};
print "@sortedindex\n";
print "@newa[@sortedindex]\n";
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I don't think this is particularly efficient, but it does give the result I think you want. It might be easier to use map, but I haven't figured map out yet.

1 0 3 2
d t x z
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is the output.