Once again, i have managed to answer my own question - here you go if you were wondering. <dtml-call "REQUEST.set('t1', 1)"> <dtml-call "REQUEST.set('t2', 2)"> Integer addition. <dtml-call "REQUEST.set('t3', t1 + t2)"> <dtml-var t3> gives you 3 string addition <dtml-call "REQUEST.set('t3', _.str(t1) + _.str(t2))"> <dtml-var t3> gives you 12 got it?