May contain letters, digits, and the underscore character (_). Punctuation and type-declaration characters are not allowed.
The exclamation point (!) can appear within the name as long as it is not the last character, in which case it is interpreted as a type-declaration character.
Must not exceed 80 characters in length.
The call cannot end with a comma. For instance, using the above example, the following is not valid:
????????a = Test(1,,)
The call must contain the minimum number of parameters as required by the called function. For instance, using the above example, the following are invalid:
????????a = Test(,1)????????'Only passes two out of three required parameters.
????????a = Test(1,2)????????'Only passes two out of three required parameters.