- First edition: http://www.oreilly.com/catalog/regex/
- Second edition: http://www.oreilly.com/catalog/regex2/
- Third edition: http://www.oreilly.com/catalog/regex3/
The second edition praises Tcl's regular expression engine: Henry's Tcl regex engine is an important step forward.Also, in Chapter 6: Crafting an Efficient Expression, Friedl says: Most of what this chapter talks about simply does not apply to Tcl. And, as the sidebar explains, Henry Spencer's Tcl regex is a hybrid DFA/NFA engine and it doesn't need most of the optimizations described in the chapter.