mxmlc: Compiler error - command line: Error: ambiguous argument list

As part of creating a as3 based preloader I needed to use "-frame start some_main_class" option. I hit the below error:

command line: Error: ambiguous argument list; unable to determine where 'frames.frame' parameters end, and default 'file-specs' parameters begin. Use '--' to terminate the parameter list, or perhaps use the '-frames.frame=val[,val]+' syntax instead.

The solution is to use a alternative syntax like the error message points to namely, "-frame=start,some_main_class".