You attempted to use a conditional compilation variable without first turning conditional compilation on. Turning on conditional compilation tells the JScript compiler to interpret identifiers beginning with @ as conditional compilation variables. You do this by beginning your conditional code with the statement:
/*@cc_on @*/
To correct this error
Add the following statement to the beginning of your conditional code:
/*@cc_on @*/
Conditional Compilation | Conditional Compilation Variables | @cc_on | @if Statement | @set Statement