# About regexp

**URL:** <https://rubytalk.org/t/about-regexp/50109>\
**Category:** ruby-talk\
**Created:** [10 November 2008 04:15 UTC](https://rubytalk.org/t/about-regexp/50109 "2008-11-10T04:15:28Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Kyung\_won\_Cheon1](https://avatars.discourse-cdn.com/v4/letter/k/e99b99/32.png) [@Kyung\_won\_Cheon1](https://rubytalk.org/u/Kyung_won_Cheon1)\
**Post date:** [10 November 2008 04:15 UTC](https://rubytalk.org/t/about-regexp/50109/1 "2008-11-10T04:15:28Z")

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> > "aaabbxccc".sub(/bb(.)c/, "\\1.upcase")

=\> "aaax.upcasecc" # I expect 'aaaXcc'

> **···**
>
> ##############  
> # Help Me^^  
> ##############  
> --  
> Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C).

---

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**Author:** ![\_Pena\_Botp1](https://avatars.discourse-cdn.com/v4/letter/_/94ad74/32.png) [@\_Pena\_Botp1](https://rubytalk.org/u/_Pena_Botp1)\
**Post date:** [10 November 2008 04:41 UTC](https://rubytalk.org/t/about-regexp/50109/2 "2008-11-10T04:41:12Z")

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# \>\> "aaabbxccc".sub(/bb(.)c/, "\\1.upcase")  
# =\> "aaax.upcasecc" # I expect 'aaaXcc'

consider,

> "\\1.upcase"

=\> "\\1.upcase"

> "\\1".upcase

=\> "\\1"

try,

"aaabbxccc".sub(/bb(.)c/) {$1.upcase}

> **···**
>
> From: Kyung won Cheon [mailto:kdream95@gmerce.co.kr]

---

<div class="post-metadata">

**Author:** ![Joel\_VanderWerf1](https://avatars.discourse-cdn.com/v4/letter/j/94ad74/32.png) [@Joel\_VanderWerf1](https://rubytalk.org/u/Joel_VanderWerf1)\
**Post date:** [10 November 2008 04:41 UTC](https://rubytalk.org/t/about-regexp/50109/3 "2008-11-10T04:41:54Z")

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Kyung won Cheon wrote:

> > > "aaabbxccc".sub(/bb(.)c/, "\\1.upcase")
> 
> =\> "aaax.upcasecc" # I expect 'aaaXcc'

\>\>\> "aaabbxccc".sub(/bb(.)c/) {$1.upcase}  
=\> "aaaXcc"

> **···**
>
> --  
> &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407