@placemats , the regional differences on Welsh aren't grammatical, but in the words used and pronunciation.
Some regional grammar is poor grammar not a variation in grammatic rules.
Where I'm from, there's a tendency to stray into an English phrase structure, but although it is common, it's not correct. (cf .Ain't got no grammar neither)
Variations in pronunciation are things like vowels sounding different or s sounding like sh. I can't get my head round people in some areas saying OK as Ock-air.
Variation of words might be:
Correct: 'A wyt ti eisiau cwpanaid o de?' (Do you want a cup of tea?)
North: 'T'isio paned?'
South 'Ti moyn dysgled?'
(Both are more 'Wanna cuppa?' but to a northerner the south walian sounds like 'are you seeking a bowlful?')
@cardibach , Cafodd ei looks like the start of something like 'Cafodd ei eni yn ...' (He was born in ...) or 'Cafodd ei adeiladu yn ...' (It was built in...).
The ei in those isn't the pronoun. If you wrote out the sentences formally, they'd be 'Cafodd ef ei eni yn...' and 'Cafodd ef ei adeiladu yn...'
The word for it will be hi or ef, depending on the subject or object. A cat is feminine, a dog masculine etc.
In my examples, if the person or building is feminine, the word for born or built will be slightly different: 'Cafodd ei geni yn...' ,'Cafod ei hadeiladu yn...'