A more thorough explanation:

A perfect obligation is a legal or moral duty that must be fulfilled by a person. It can be imposed by law, contract, promise, social relations, courtesy, kindness, or morality. It is a legally enforceable obligation that is recognized and sanctioned by positive law.

For example, if you sign a contract to pay rent every month, you have a perfect obligation to pay that rent. If you fail to pay, your landlord can take legal action against you to enforce the obligation.

Another example is a loan agreement that requires the borrower to make monthly payments. The borrower has a perfect obligation to make those payments, and the lender can take legal action if the borrower fails to do so.

These examples illustrate how a perfect obligation is a legally enforceable duty that must be fulfilled by the obligated party.