I found it very useful years ago to print out the Tcl re_syntax.n manual
page, and read it very slowly, repeatedly, on one summer afternoon years
ago. It also takes practice to really become good with regular
I find that it's useful to re-read other things many times in general.
Somehow the picture in my mind forms differently after getting more
context in later paragraphs, and revisiting my earlier context.
P.S. Regular expressions are not the solution to everything. Sometimes
a parser written in Tcl works better than regular expressions.