# Regular expression

**URL:** https://community.mp3tag.de/t/regular-expression/7482
**Category:** Support
**Created:** [November 16, 2008, 1:09pm UTC](https://community.mp3tag.de/t/regular-expression/7482 "2008-11-16T13:09:26Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![vkostas](https://community.mp3tag.de/user_avatar/community.mp3tag.de/vkostas/32/227_2.png) [@vkostas](https://community.mp3tag.de/u/vkostas)
#### Post date: [November 16, 2008, 1:09pm UTC](https://community.mp3tag.de/t/regular-expression/7482/1 "2008-11-16T13:09:26Z")

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I want to use first letter of one tag (band) to format another tag and want to replace the first letter to # if not alphabet character using regular expression  
$regexp($left(%band%,1),(?([A-Z])$0|#))  
The result is blank. Any idea?  
I've tried $regexp($left(%band%,1),[^A-Z],#) also but I get error ☹

Thank you,  
Victor

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### Author: ![Florian](https://community.mp3tag.de/user_avatar/community.mp3tag.de/florian/32/5759_2.png) [@Florian](https://community.mp3tag.de/u/Florian)
#### Post date: [November 16, 2008, 1:45pm UTC](https://community.mp3tag.de/t/regular-expression/7482/2 "2008-11-16T13:45:47Z")

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$regexp($left(%band%,1),^\d,#)

Kind regards,  
Florian

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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, 12:21pm UTC](https://community.mp3tag.de/t/regular-expression/7482/3 "2026-02-09T12:21:12Z")

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