Identifiers
Identifiers are simply names for user-defined variables and functions.
Identifiers can be composed from lower and upper-case letters (from the
English alphabet), underscore _
and numbers, however an identifier
cannot begin with a number. Line and upper-case symbols differ (Pine is
case-sensitive). Here are some examples of valid identifiers:
myVar
_myVar
my123Var
MAX_LEN
max_len