$r1 = $c; # $r1 Used only once.
# ....
$lambda_next = ($lambda_max + ($ks * $rL3)) * (1 - $kdeg); # $rL3 used only once.
# ....
$cro_next = ($cro_max + ($ks * $OR1)) * (1 - $kdeg); # $OR1 used only once.