# Regular Expressions, change from 2.47? to 2.49

**URL:** https://community.mp3tag.de/t/regular-expressions-change-from-2-47-to-2-49/12118
**Category:** Support
**Created:** [June 8, 2011, 6:05pm UTC](https://community.mp3tag.de/t/regular-expressions-change-from-2-47-to-2-49/12118 "2011-06-08T18:05:28Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![Zoofield](https://community.mp3tag.de/user_avatar/community.mp3tag.de/zoofield/32/136_2.png) [@Zoofield](https://community.mp3tag.de/u/Zoofield)
#### Post date: [June 8, 2011, 6:05pm UTC](https://community.mp3tag.de/t/regular-expressions-change-from-2-47-to-2-49/12118/1 "2011-06-08T18:05:28Z")

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there appears to have been a change in using character classes with anchors within negative lookbehind assertions.

example, around 2.47 this worked (?\<!^|\s|\d) Now with 2.49 this does not.

Separately, (?\<!^) , (?\<!\s\d) , both work. Is this a bug? Or, is there a solution to my query?

This is the full regexp that did work and now does not. (?\<!^|\s|\d)(.)([^\W\d\_])(?!.|\s|$)

Thank-you in advance!

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### Author: ![dano](https://community.mp3tag.de/user_avatar/community.mp3tag.de/dano/32/6_2.png) [@dano](https://community.mp3tag.de/u/dano)
#### Post date: [June 8, 2011, 7:19pm UTC](https://community.mp3tag.de/t/regular-expressions-change-from-2-47-to-2-49/12118/2 "2011-06-08T19:19:32Z")

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Alternations in a lookbehind expression need to be of equal length in Mp3tag, so this expression never really worked.  
The only change is that now it raises an error message.  
See discussion [here](https://community.mp3tag.de/t/10616/7).

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### Author: ![system](https://community.mp3tag.de/uploads/default/original/2X/c/ce7035d426cb755a7916793326d23b465222a407.png) [@system](https://community.mp3tag.de/u/system)
#### Post date: [February 9, 2026, 12:23pm UTC](https://community.mp3tag.de/t/regular-expressions-change-from-2-47-to-2-49/12118/3 "2026-02-09T12:23:09Z")

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