A more thorough explanation:

Perpetua is a legal term that refers to a type of exception, plea, or objection in Roman and civil law.

One example of an exceptio is exceptio peremptoria, which is a peremptory exception that forever destroys the subject matter or ground of the action. This includes exceptions such as exceptio doli mali, which is a defense or plea of fraud, and exceptio metus, which is a defense or plea of fear or compulsion.

Another example is exceptio non numeratae pecuniae, which is an exception or defense that money was not paid. This exception was used in Roman law when a debtor had acknowledged receipt of a certain sum of money but had not actually received it. The debtor could plead exceptio non numeratae pecuniae to elide the demand for repayment, unless the creditor proved that they had advanced the money.

These examples illustrate how exceptio can be used as a defense or plea in legal proceedings to negate a claim or assert a right.