Customise speech assistant

OSX's speech assistant must be the most underrated feature of any product ever.

The complexity of speech recognition algorithms is colossal. I have been tracking their progress for years, as I have injuries from using the computer and depend upon speech recognition.

What is more, the recognition accuracy seems to be at least as good as Dragon/Nuance, without the appalling buggy front-end. I don't even require a custom microphone any longer. The MacBook's inbuilt microphone seems to be enough.

So I cannot say I am not grateful.

However, some things still drive me up the wall. If I say 'on' it will usually interpret 'en'. Which isn't even in the English language. And if I say 'script', it inserts 'prescription'. Which makes me want to punch something. If I want to say 'prescription' I will say 'prescription'.

Is there some way to disable these idiot presumptions? Some kind of "post translation" scripting I could do? Some way of intercepting the translated text and modifying it before it reaches the target app?