1007 - Expected a variable at this location.

Description
A variable was expected, but some other symbol was encountered.
Example
Config:
Using( 'String' )
Output:
c:\test\fbuild.bff(1):(8) FASTBuild Error #1007 - Using() - Expected a variable at this location. Using( 'String' ) ^ \--here
Fix:
Using( .MyStruct ) // A previously defined variable