Perennial rhymes with:
bicentennial, biennial, centennial, decennial, millennial, quadrennial, triennial, bicentennial, biennial, centennial, ceremonial, colonial, company'll, decennial, intracranial, lineal, matrilineal, matrimonial, menial, millennial, patrilineal, quadrennial, testimonial, triennial
Perennial sounds like:
parmele, parmelee, parmley, parnell, parnella, parrinello, perennially, pernell, pernella, primal, primly, prunella, purnell