[L1 ] - NEM This link is dead for me on 2 June, 2005. This [L2 ] article from comp.lang.tcl certainly looks relevant, however.
[Wiki page on e-mail addresses]
[different meanings of "regular expressions"]
[ Perl disease]
[When REs go wrong]
05Apr03 Brian Theado - For XML, I'm guessing the title of this page is referring to one-off regular expressions, but see [L3 ] for a paper describing shallow parsing of XML using only a regular expression. The regular expression is about 30 lines long, but the paper documents it well. The Appendix includes sample implementation in Perl, Javascript and Flex/Lex. The Appendix also includes an interactive demo (using the Javascript implementation apparently). The demo helped me understand what they meant by "shallow parsing". For a Tcl translation, see XML Shallow Parsing with Regular Expressions.
Why are regular expressions not suited for parsing email addresses? "Regular expression to validate e-mail addresses" comments on this.
A few more comments appear in "The Limits to Regular Expressions" [L4 ] and "Regular Expressions Do Not Solve All Problems" [L5 ], themselves descendants of Jamie Zawinski's notorious judgment [L6 ] REs multiply, rather than solve, problems.