the name of a macro variable within
double quotation marks but without an ampersand
the name of a DATA step character
variable, specified with no quotation marks, which contains a macro
variable name
a character expression that constructs
a macro variable name
Details
The SYMEXIST function
searches any enclosing local symbol tables and then the global symbol
table for the indicated macro variable and returns 1 if the macro variable is found or 0 if the macro variable is not found.
For more
information, see theSYMEXIST Function in SAS Macro Language: Reference.