4.2.2 Evaluating forms without printing results

:eval-before

Trace keyword

This option allows you to supply a list of forms for evaluation upon entering the traced function. The forms are evaluated after printing out the arguments to the function, but unlike :before their results are not printed.

:eval-after

Trace keyword

This option allows you to supply a list of forms for evaluation upon leaving the traced function. The forms are evaluated after printing out the results of the function call, but unlike :after their results are not printed.