Personalization strings are enclosed within double percentage delimiters; for example,
%%string%%. However, these delimiters should not be included when used in an AMPscript function (refer to Attributes). The containing string is case-insensitive.
NOTE: If the attribute name contains a non-alphanumeric character, then it must be enclosed in square brackets.
%%[ var @firstName, @age set @firstName = [First Name] set @age = Age ]%%