You suppose you may have an idea: your still partially human mind figures that if you can create enough of a sudden thrust from your tail, you might launch yourself high enough to get out of here. Luckily, your captor has never seen you jump so he will assume you are strictly ground-bound. You slither around your cage some more, waiting for him to come glee over your predicament as usual. When he finally comes to your cage, he lifts the grate for a moment and throws in some food for you, keeping the grate open for a moment to laugh at you. Then, you quickly make a move he would never have expected: you coil your tail, tense whatever muscle you have and dart straight at his face with a loud hiss!
Before he manages to close your cage you've already sunk your fangs into his face, and he screams loudly while trying to get you off. You just drop to the floor and slither for the nearest open door while he's in agony from your bite. It's a question how long you will be able to escape him, though...just a matter of seeing how effective your venom will prove.