The future perfect and the perfect subjunctive in Latin versification: a metrical or a morphological problem?

Since there are no special problems for the Latin future perfect or the perfect subjunctive to fit in the verse line, it could be admitted that Latin classical poetry reveals the actual use of language. at first sight, there seems to be a preference for the forms in -- eris . However, the relative high number of forms in -- eris in both Ovid's and Horace's writings would rather point to a confusion in the current language, once proved that, against an extended opinion among scholars, there is no lengthening before caesura in these cases. Adapted from the source document