Gov. Perry was referrng to what he (mistakenly) thought was a "right" to secede as included in our 1845 Annexation Agreement, i.e., a "right" that distinguishes Texas from all other states. No such provision appears in our Annexation.
As I have read numerous version of his statement, I do not believe he was referring to Texas' sovereign right to secede as vested in the U.S. Constitution - which is a legitimate "right" to secede applicable to all states.
Nice to hear from you again, Penny. Ya been absent for a while, sorta like me.