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.
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:
Test 1,,
The call must contain the minimum number of parameters as required by the called subroutine. For instance, using the above example, the following are invalid: