[Python] Matching end of string or ; in regex

Why does the following regex not match the last occurrence of the search word?

(?i)(^|,|\s*old\s*($|


This matches the first and second old, but not the third:

One,old;Two,old;old
^ ^ ^
match match \_ no match


However, if I remove the last ; ((?i)(^|,|\s*old\s*$), it does match the last occurrence.

P.S. I'm using Python.

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