executing a wedged cell can cause a loop

with this code ```ts const phoneNumberRegex = /^\(?\d{3}\)?[\s.-]?\d{3}[\s.-]?\d{4}$/; phoneNumberRegex.exec("555-867-5309") ``` the regex gets wedged (?!) when there's not a match. If you then change the input so there is a match, there's a loop that spews "already executing" messages to the logs.