An expression includes a variable that has not been defined with a var statement or that has a misspelled name, and the code is compiled in fast mode. Programs compiled in fast mode must have all variables explicitly declared.
Fast mode can be turned off for programs compiled with the command-line compiler.
To correct this error
Make sure to define all variables.
Make sure all identifiers are spelled correctly.
Compile the program with the /fast- option to turn fast mode off. (For command-line compilation only.)