Hi Aurel,
MasmBasic is strong on strings (but a bit weak on numbers). So yes, a fast tokeniser would be possible.
With
Recall somefile, some$() you load your source into a string array, then you need to parse each line for labels, keywords, arguments etc.
Instr() is your friend. And many more functions; besides, you can use plain assembler, too. These functions are really, really fast, about twice as fast as equivalent C code.
Do you have an example of a source using your interpreted language?