Here are some examples, all in 1st person singular active:
currere, 'to run' has the following forms: present tense curro, perfect tense cucurri. That's decently regular, and have several verbs that follow this form.
However, there is also
pellere, 'to push'. Present tense pello, perfect tense pepuli
cadere, 'to fall. Present tense cado, perfect tense cecidi.
Now, the actual reduplication aside, cucurri works out well because the vowels are the same. But we see that in pepuli and cecidi, the vowels don't carry over in the reduplication.
I have read some articles that just say that from some form of Proto-Latin (or rather Proto-Indo-European) that adding the reduplicated consonant with an 'e' vowel is just the preferred way that they did it. That statement doesn't have much substance in my mind, but we can also see that cucurri doesn't follow that, as well as a few others.
It could be easy to say that maybe if the vowel is a 'u' it doesn't change the vowel, while 'i' would, as this is what happens a lot. But there we see that pepuli makes that not work either.
Does anyone have any tips or can recommend any books/articles/resources to help me address the morphology or morphophonology that is happening here? Thank you very much.
(cross-posted to Latin community)