I already posted an example of another way to do this subroutine at Re: Trudging along the learning perl path..

Below, I have modified your code which uses array indices and "looks forward" to the next element. I am sure you wondered why you needed to sort the array yet again? That is because the index of -1 means the last element of the array in Perl and that caused the largest value to appear at the beginning of the @unique array.

Here is another way of using "look ahead" indicies.... compare with your code...

use warnings;
use strict;

my @arr = (29,24,0,24,24,12,0,10,29,10,19,17,15,13,1,12,12,24,31);


sub del_duplicate 
{
    my @sorted = sort{$a <=> $b} @_;
    my @unique;
    
    my $current;
    my $next;
    
    foreach my $index (0..@sorted-2) 
    {      
        $current = $sorted[$index];
        $next    = $sorted[++$index];
        if ($current != $next) 
        {
            push @unique, $current;
        }
    }
    
    # this is a "fix-it" statement after the loop
    # in order to get the last element of @sorted
    
    push @unique, $next;  # add the last value
    
    print "@unique\n";
}

del_duplicate(@arr); #0 1 10 12 13 15 17 19 24 29 31
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You are trying to learn and are writing code. Beginners don't write perfect code and by the way sometimes experts don't either!

Update: There is a problem with the above code if say, there is only a single element in @arr, i.e., @arr=(29);. This is one of several reasons why I would discourage iterating over array indices in Perl code.

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