This function evaluates the expression expr and traps any run-time or parser errors resulting from evaluation of the expression. It also allows non-local exits from functions invoked by the expression using throw. If the optional argument noerr is specified and non-zero, then any error messages can be suppressed as with eval.

catch returns zero if the expression is evaluated without error. If there was an evaluation error, catch returns 1. If throw was executed during the evaluation of expr, catch returns the value of throw, which must be non-zero.