generator is "expression", which accepts a "from" value in the form of a simple regular expression containing the range expression "[a-zA-Z0-9]", and the length expression "a{length}".

Examples:

from             | value ----------------------------- "test[0-9]{1}x"  | "test7x" "[0-1]{8}"       | "01001100" "0x[A-F0-9]{4}"  | "0xB3AF" "[a-zA-Z0-9]{8}" | "hW4yQU5i"²