there is no such thing as a " perfect rhyme "
You are absolutely right, i had seen you use the term before so was using it as a short hand term...
instead lets rephrase perfect to mean, a rhyme scheme and meter like eminem 'infinite'...
i.e.
count of syllables match between lines that rhyme
majority of syllables in each line are part of a compound rhyme
the same multiple syllable rhyme is used more than twice in a row
with that kind of rhyme when executed well what is the chief disadvantage from a technical standpoint?