Just a few regex links I remember in case they are useful:

• Teaching Regular Expression Pattern Matching
• The craziest RegExes you ever created
• Negating Regexes: Tips, Tools, And Tricks Of The Trade
• Training non-programmers in Perl regexps
• Style question: regex versus string builtin function
• Yet Another Rosetta Code Problem (Perl, Ruby, Python, Haskell, ...)
• Re: RFC: Self Assessment Perl
• Re: regexp match count (goatse)

• Perl Training Australia - Regular Expressions in Perl 5.10
• Mastering Regex in Perl slideshow

References Added Later

• PPI - Parse, Analyze and Manipulate Perl (without perl)
• PPR by TheDamian - a single regular expression suitable for matching entire Perl documents
• Re: Knowing when a code string contains code that will be executed at compile-time/end? - kcott and haukex discuss the differences between PPI and PPR

• Re^3: Replace empty alt tag on <img> tag -- dont use a regex by Discipulus (2022)

• Regex, the jungle survival skill by mmkstarr (2016)

See Also

• Re^2: Substitution remove all before (Parse HTML/XML with Regex References)

Updated: Extra references were added later.