package Average; # D e c l a r e  a  p a c k a g e
                # A v e r a ge  a  l i s t  o f  g r a d e s

sub av {
$total = 0;
@grades = (3,4,5);

$num_of_grades =$#grades + 1;
foreach $grade ( @grades ) {
     $total += $grade;
}
 $res = $total/$num_of_grades;   #  W h a t  g e t s  r e t u r n e d
#print $res;
return;
}
#&av;

##</code><code>##



#!/usr/bin/perl

use warnings;
use Average;

$d = Average::av($res);
print $d;


##</code><code>##


Name "main::res" used only once: possible typo at ./ave.pl line 6.
Use of uninitialized value $d in print at ./ave.pl line 7.