Rules for names in identifiers used in policies
The names of identifiers in the named expression, HTTP callout, pattern set, and rate limiting features must begin with an ASCII alphabet or an underscore (_). The remaining characters can be ASCII alphanumeric characters or underscores (_).
The names of these identifiers must not begin with the following reserved words:
The words ALT, TRUE, or FALSE or the Q or S one-character identifier.
The special-syntax indicator RE (for regular expressions) or XP (for XPath expressions).
Expression prefixes, which currently are the following:
Additionally, the names of these identifiers cannot be the same as the names of enumeration constants used in the policy infrastructure. For example, the name of an identifier cannot be IGNORECASE, YEAR, or LATIN2_CZECH_CS (a MySQL character set).
Note: The Citrix ADC appliance performs a case-insensitive comparison of identifiers with these words and enumeration constants. For example, names of the identifiers cannot begin with TRUE, True, or true.