There is always such questions when using TK's text widget. Type Tab in the Text Widget, which will not change the FOCUS, only there is a Tab (its value can be set).
After reading the text of the text, there is no corresponding property, you can change this behavior. A program written by yourself can only jump in each Text to jump with each TEXT. (Shift - tab is still available).
Today, I saw Mastering Perl / TK about FOCUS, and I found that I will write it in a beginning. Use Tab to transfer FOCUS, but when you encounter text, use Ctrl-Tab.