Code:
#showtooltip
/cast [mod:shift, stance:1] Rend; [stance:1] Thunder Clap
/cast [mod:shift, stance:2] Piercing Howl; [stance: 2] Thunder Clap
/cast [mod:shift, stance:3] Piercing Howl; [stance: 3] Pummel
I believe that's what you're looking for. And, since I'm compulsive about character counts:
Code:
#show
/cast [mod:shift, form:1] Rend; [mod:shift, form:2/3] Piercing Howl; [form:1/2] Thunder Clap; [form: 3] Pummel