Hi All! I have been given a task of modifying someone else's program. The program i have to modify does not use strict and warnings. So I decided to put them in, and I am having all sorts of error messages. Anyway I fixed most of these errors, but there is a a bit that I just cannot fix and also I don't understand the syntax. Could you help me figure out what the program is trying to do? Here is the code (@ldx array is a multidimensional array and I cannot put it here because it is quite big): 
my $ct=0;  my @nxxult = (); my @Ultmnsort = (); my @indexUlt = ();
for(my $rn=4;$rn<=32;$rn +=4)
  {
    for(my $bn=1;$bn<=$row[0];$bn++)
    {
       $nxxult[$bn]=$ldx[$bn][$rn];
    }
       #@indexUlt=sort{$nxxult[$a]<=>$nxxult[$b]} 0 ... $#nxxult;
        $Ultmnsort[$ct]=$indexUlt[0];
        $Ultmxsort[$ct]=$indexUlt[$#indexUlt];
        $ct++;
        [$#indexUlt]\n");
     print TEST3 ("ct = $ct\n");
  }

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This is the syntax I don't understand (I now it is doing some kind of sorting but this is where the program is giving error messages): 
#@indexUlt=sort{$nxxult[$a]<=>$nxxult[$b]} 0 ... $#nxxult;

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Here is the error message: 
Use of uninitialized value in numeric comparison (<=>) at C:\SORT.pl l
+ine 791, <AREA> line 22371.

[download]

In reply to Assist in understanding old code by ozgurp

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