Three other forms exist for the copula ê: éra (+ANT), ser (after a verbal particle, after another verb and after prepositions) and sérba (+ANT, if one of the conditions for ser applies). I don’t consider the acrolectal forms foi, stevi and tevi to be perfectives of ê, sta and ten(e), but perfective partner verbs for ê, sta and ten(e). In fact, there is no formal rule for the formation of perfective forms to other stative verbs.
A lot of verbs have (along with the regular anterior with -ba) irregular, acrolectal forms, that are borrowed from Portuguese, cf. benba ~ binha (ben 'come’), debeba ~ devía (debe 'must’), kreba ~ kria (kre 'want, love’), ten(e)ba ~ tinha (ten(e) 'have’). From a synchronic point of view, these constitute cases of weak suppletion.
Source: Lang et al. 2012
Source: Lang et al. 2012