I have heard that some Chinese actually put cut up rat in their salad. That snake must have liked rat.

It is most likely that the snake was attracted to a meat smell on the veggies. The snake can digest the vegetable matter. They do it all the time when they digest the stomach contents of their prey. That is where they get a lot of their vitamins and minerals. However straight veggies would not apeal to a normal healthy snake.
There are no vegetarian snakes.

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Merlin,
What's Life Without A Little Magic!