To distinguish strings from integers, string variable
names must end in a $. Variable names must start with a letter and
can include any sequence of letters, digits, and underscores. Function
and command names must not be used as a variable name. Variable names
are not case sensitive and are converted to uppercase by the interpreter.
A common mistake is to use a command or function
name as a variable. To avoid using these reserved words, ZBI-Developer
can be a useful resource. Reserved words are highlighted making
it easier to spot this occurrence and thus, saving debugging time.