The Texas Constitution allows spending increases, but not as much as Perry and other Republicans and Democrats want.
The article notes: "The House's chief budget writer, Jim Pitts, R-Waxahachie, said he isn't sure if there are enough votes in the House to break the spending limit but that it will be necessary to do so if lawmakers want to achieve certain expensive goals before the session ends."
Yes, when you have expensive goals, you often have to spend a lot.
Instead of respecting constitutional limitations, Republican and Democratic lawmakers usually try to find ways around them.
In last year's election, a number of Libertarian candidates for the Texas legislature proposed cutting state spending by at least $25 billion.