Calls a named event handler directly. If the function cannot be found or the found handler did not want to handle the event, #f is returned. Otherwise, the return value is the return value of the event handler.
The in and event arguments are passed on to the keymap handler procedure if one is found.
If try-chain? is not #f, keymaps chained to this one are searched for the function name. If the function is not found and try-chain? is #f; an exception is also raised, but the exception handler cannot escape (see Exceptions and Continuation Jumps).