use strict;
use warnings;


sub get_max_index
{
    my $arrayRef = shift;
    
    my $imax = $arrayRef->[0]; #don't modify @arr
    
    for (@$arrayRef){
            $imax = $_ if $imax < $_;
        }
    return $imax;  
}

my @arr = (1..10);
my $ans = get_max_index(\@arr);  #pass reference to array!
print"$ans\n";