My PhD student was still feeling uncomfortable with #regex, so I searched and found these awesome regex games that can help you improve your regex-fu and help you have some fun during your daily commute:
https://www.the-regex-game.com/?level=integer
and this imho is more geared towards beginners:
At a past position, the team I was on had a #regex that was several kilobytes in length in several products. It was the stuff of nightmares! 
We only managed by splitting their definition strings into multiple pieces that were assembled kind of like a puzzle. 
That said, it was also an amazing learning experience and taught me about things to be extremely careful about, like don’t go too deep with the nesting of groups, and definitely don’t sprinkle deeply nested groups with the Kleene star or anything else that is unbound in length or repetition. 
(I still love #RegularExpressions for their power, though. 
)
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@tripleo You’re thinking of #Perl’s “taint mode” (stop your teenage giggling), where outside data is untrusted unless it’s the extracted subpattern match in a #RegularExpression.
It’s only enabled under certain conditions. Read about it in the `perlsec` manual page: https://perldoc.perl.org/perlsec#Taint-mode
I see a lot of unnecessarily specific regexs (typically excessive captures & pointless `.*$`) being used. Logic says they'll be slower so I spent about 90 seconds testing an example on 3 in-browser JS benchmark apps.
Comparing:
`/^(Hello), this is a string (.*)$/` to
`/^Hello, this is a string /`
the latter is 1.5-5x faster on all 3 apps.
#RegEx #RegExp #RegularExpression
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#Perl has supported pluggable replacements for its #RegularExpression engine since the release of v5.10 in 2007: https://perldoc.perl.org/perlreapi
An @ietf compliant I-#Regexp subset would be very helpful for @Perl #developers implementing specifications like the draft #JSONPath standard: https://datatracker.ietf.org/doc/draft-ietf-jsonpath-base/
(There is already a JSONPath #CPAN module: https://metacpan.org/pod/JSON::Path) https://cosocial.ca/@timbray/110714888717469041
@jernej__s @malwareminigun / \p{Quotation_Mark} solved \p{Quotation_Mark} /x #Perl #regex
(Note that doesn’t work with software using the #PCRE Perl “Compatible” #RegularExpression library because its #Unicode support is worse: https://www.pcre.org/current/doc/html/pcre2unicode.html#:~:text=Only%20the%20short%20names%20for%20properties%20are%20supported)
@regehr @commodore @dev There is even a (low-severity, a/k/a “cruel”) #PerlCritic policy to discourage everything but $_, @_, $], and numbered #RegularExpression capture variables: https://metacpan.org/pod/Perl::Critic::Policy::Variables::ProhibitPunctuationVars
https://metacpan.org/pod/Perl::Critic::Policy::Variables::ProhibitMatchVars already protects you against the performance-sapping $`, $&, and $' match variables
And you can configure your own prohibited list with https://metacpan.org/pod/Perl::Critic::Policy::Variables::ProhibitEvilVariables
@james #macOS #Safari “finally” introduced extensions on the desktop in 2015 and third-party ad blockers followed shortly after. They would later revamp extensions to make it easier to port Web Extensions from #Firefox and #Chrome. The Content Blocker API is specifically for performant and energy-efficient sets of #RegularExpression-based URL and resource type filters.
@ChristosArgyrop @Perl The hash lookup in that article’s second example says it’s mainly useful for exact string matching. The `for` topicalizer pattern is still good for arbitrary conditions like the #RegularExpression matches I list, but it could just as easily use `isa` for class matching, or whatever.
#Regex question: I want to match strings of the form xyyx, where x and y ∈ [a-z] but x != y. So abba, cffc etc. should match but dddd shouldn't.
"([a-z])([^\1])\2\1" doesn't seem to work and also matches dddd (at least in Vim).
#EmacsTip: It is always better to use #Rx instead of raw #RegularExpression, because they are error-prone, especially the escapes. But if you need to use raw #RegularExpression, install #Relint, a #RegularExpression linter for #EmacsLisp. Just run relint-current-buffer in your buffer, it will find most of your #Regex bugs.
