(alexandria.0.dev:if-let bindings &body (then-form &optional else-form))
|Function: Creates new variable bindings, and conditionally executes either THEN-FORM or ELSE-FORM. ELSE-FORM defaults to NIL. BINDINGS must be either single binding of the form: (variable initial-form) or a list of bindings of the form: ((variable-1 initial-form-1) (variable-2 initial-form-2) ... (variable-n initial-form-n)) All initial-forms are executed sequentially in the specified order. Then all the variables are bound to the corresponding values. If all variables were bound to true values, the THEN-FORM is executed with the bindings in effect, otherwise the ELSE-FORM is executed with the bindings in effect.