for my $aref ( @lnPAM ) {
        $_ /= ( $mutRate * 100 ) for @$aref;
    }

##</code><code>##

@a = map[ map int(rand$_), 1 .. 10],1..10;;
cmpthese -1,{
    a=>q[ map $_ /= 1, @$_ for @a; ],
    b=>q[ for my $r( @a ){ $_ /= 1 for @$r } ], 
};;
     Rate    b    a
b 52726/s   -- -25%
a 70388/s  33%   --

##</code><code>##

while( abs( $mutRate - 0.01) > 1e-16 ) {
    ++$iter;
    $k *= $mutRate * 100;
    map $_ /= ( $mutRate * 100), @$_ for @lnPAM;
    @matrix = map[ map exp( $_ ), @$_ ], @lnPAM;
    $mutRate = sum map{ $freq[ $_ ] * ( 1 - $matrix[ $_ ][ $_ ] ) } 0..19;
    printf "After %d iteration(s), k=%f, RateMutation=%f\n", $iter, $k, $mutRate;
}

##</code><code>##

while abs(RateMutation - 0.01) > DBL_EPSILON do
    iter := iter + 1;
    k:= k * RateMutation * 100:
    lnPAM1 := lnPAM1 / (RateMutation * 100):
    PAM1 := exp(lnPAM1):
    RateMutation := sum(Freq[i] * (1 - PAM1[i,i]), i= 1..20);
    printf('After %d iteration(s), k=%f, RateMutation=%f', iter, k, RateMutation);
od: