I created https://www.wikidata.org/wiki/Q23809765 .
As part of it I entered a Foundational Model of Anatomy ID.
I first entered it as FMA23377 as I have seen the ID that way at other places. Wikidata however formats it's Foundational Model of Anatomy ID's as 23377. It even has this format specified in the format as a regular expression attribute of Foundational Model of Anatomy ID.

However it doesn't tell me that the data I put into the field violates the format it defined itself as format as a regular expression. I therefore propose that in the future it checks whether data that's entered conforms to the specified format.