[GiNaC-list] using modulo and expanding

is there a way to use modulo over an expression? for example: 3*k1^2+4*k1*k2+1231231*k1 mod 2= k1^2+k1 all I really want is to work with polynomials over Z_2 so with subs I can do subs(a,$1^2=$1) but some times it's not enough cause I might run into something with power more than 2 would subs(a,$1^$2=$1) be enough??? I'm not using ginsh but c++ any help???