Tried this:

my $j = 1;
my $p = $s[1]; #values are present starting from 1st index
while ($j != $n - 1) {
    if ( ($p < $s[$j+1]) || ($p == $s[$j+1]) ) {
    }else{
        $p = $s[$j+1];    
    }
    $j++;
}
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i guess that $p should keep the minimum value of the array, but the question is how to get its index.

well this code is broken in too many ways...

But to keep it short, you have to set a variable $min_idx=$j+1 in the else track.

Let me propose something more perlish

use strict;
use warnings;
use Data::Dump;


my @s= map { int rand 100 } 1..10;
dd \@s;

my $min_idx = 0;
my $idx     = 0;
my $min     = $s[0];

for my $value (@s) {
  ($min,$min_idx)=($value,$idx) if $value < $min ;
  $idx++;
}

dd $min,$min_idx;
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out:

[96, 40, 65, 98, 46, 17, 2, 60, 12, 67]
(2, 6)
[download]