regsub and regexp usage in tcl

 

 so in order to reg () in tcl; we needs to use regexp -- {\(\)} $express

　　　　　　　　　　　　　　　　or use: regsub -- "\\(\\)" $express 

 https://stackoverflow.com/questions/14237376/how-to-use-regexp-to-match-a-parentheses-in-tcl