Isint()
This function will return 1 (TRUE) if the argument is a valid integer and 0 (FALSE) if it is not. Integers have an optional leading + or - sign followed by digits only.
Examples
> say isint(22223.0000)
You say "0"
> say isint(+77)
You say "1"
> say isint(22 L)
You say "0"