you should let the snake stay in the garden, as the snake eats pests. there's a natural balance of predator and prey in nature. it's good to try to restore this balance in our gardens as well.
what kind of green worms do the damage? there are predatory wasps which eat many insect larvae (worms)... you can attract them to your garden by planting saunf or clover. they will by attracted by the smell of the saunf, but when they see the worms nearby, they will eat the worms.
you can also spray your tomatoes with salt water on a regular basis (not the root area, just the leaves/fruits), which makes the worms sick, so they will avoid it. or sprinkle cornmeal (maki atta) around the base of the plant- the worms don't like to cross it.
there are many natural remedies to reduce pests in our garden that don't involve pesticides. look for books and websites on natural gardening for more info.