# Which Regular Expression engine and syntax is used by Mp3tag?
**URL:** https://community.mp3tag.de/t/which-regular-expression-engine-and-syntax-is-used-by-mp3tag/47713
**Category:** Support
**Created:** [January 30, 2020, 10:39am UTC](https://community.mp3tag.de/t/which-regular-expression-engine-and-syntax-is-used-by-mp3tag/47713 "2020-01-30T10:39:48Z")
**Posts on this page:** 6
**Page:** 1
### Author:  [@mville](https://community.mp3tag.de/u/mville)
#### Post date: [January 30, 2020, 10:39am UTC](https://community.mp3tag.de/t/which-regular-expression-engine-and-syntax-is-used-by-mp3tag/47713/1 "2020-01-30T10:39:48Z")
I read that MP3Tag uses Perl's regular expression engine.
Can anyone tell me which version of Perl is MP3Tag using? TIA.
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### Author:  [@Florian](https://community.mp3tag.de/u/Florian)
#### Post date: [January 30, 2020, 11:20am UTC](https://community.mp3tag.de/t/which-regular-expression-engine-and-syntax-is-used-by-mp3tag/47713/4 "2020-01-30T11:20:26Z")
I'm not using Perl (as the Perl engine) in Mp3tag — it's all C++. As regular expression engine I'm using Boost.Regex which has a perl regular expression syntax.
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### Author:  [@mville](https://community.mp3tag.de/u/mville)
#### Post date: [January 30, 2020, 1:43pm UTC](https://community.mp3tag.de/t/which-regular-expression-engine-and-syntax-is-used-by-mp3tag/47713/7 "2020-01-30T13:43:13Z")
I have spent days working on an action group that I cannot get working.
I have just discovered, at regular-expressions.info, that there are Lookbehind limitations in Boost and/or Perl.
If I know which version(s) MP3Tag is using, I can check whether the regex feature I wish to use is supported, without spending days trying to get unsupported regex features to work.
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### Author:  [@Florian](https://community.mp3tag.de/u/Florian)
#### Post date: [January 30, 2020, 4:21pm UTC](https://community.mp3tag.de/t/which-regular-expression-engine-and-syntax-is-used-by-mp3tag/47713/8 "2020-01-30T16:21:02Z")
Yes, as far as I know lookbehind must be fixed length. [Here](https://www.boost.org/doc/libs/1_70_0/libs/regex/doc/html/index.html) is the documentation for Boost.Regex included in Boost 1.70 which I'm _currently_ using.
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### Author:  [@mville](https://community.mp3tag.de/u/mville)
#### Post date: [January 30, 2020, 4:47pm UTC](https://community.mp3tag.de/t/which-regular-expression-engine-and-syntax-is-used-by-mp3tag/47713/9 "2020-01-30T16:47:27Z")
Many thanks for the confirmation and link.
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### Author:  [@system](https://community.mp3tag.de/u/system)
#### Post date: [August 26, 2025, 1:12pm UTC](https://community.mp3tag.de/t/which-regular-expression-engine-and-syntax-is-used-by-mp3tag/47713/10 "2025-08-26T13:12:13Z")
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