To be in the safe side, Next time when you write something like that consider adding some extra checking in your sub for example

sub covariance {
    my ($arraylref, $array2ref) = @_;
    if ( ref($arraylref) ne 'ARRAY' or ref($array2ref) ne 'ARRAY') {
     return "expecting array reference to be passed";
   }
}

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In reply to Re: covariance calculation by ahmad
in thread covariance calculation by vis1982

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