infix format nemerle macro

say i need unequivocally special computation operator. competence implemented following macro:

macro @<<!(op1, op2)
{
    <[ ( $op1 * $op2 ) ]>
}

and i like

def val = 2 <<! 3

and the work.

but i unequivocally wish 'english'-like user dsl im building now:

macro @multiply(op1, op2)
{
    <[ ( $op1 * $op2 ) ]>
}

and i try like

def val = 2 greaten 3

compiler fails 'expected ;' error

what problem? i exercise infix-format macro?

code1