Úf! It took some time and you may no longer need it. My double agents in Lleida inform that "periol" is (they actually say "is", not "may") also "poriol" or "poliol", that is, "poleo menta" in Spanish and, I believe, Pennyroyal in English, Mentha pulegium in Latin. It may either be a typo or just the way it's said in some area of the Principat. My level of confidence is based on the source of the "poliol" info, quite reliable: my mole at the Universitat de Lleida.
Cheers and luck :-) P

Oh, and this may be enlightening, Menorcan herbs, you'll find Poriol here: www.caib.es/conselleries/educacio/dginnova/CPR/cprmenorca/c...