Before performing addition operation ,check whether that array index is having value or not using define function.

Your code,

for my $valNum (0 .. $total){
    
    $mean += $value[$valNum];
    
}
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Change the loop like the following,

for my $valNum (0 .. $total-1){
    if(defined($value[$valNum]))
    {
    $mean += $value[$valNum];
    }
}
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