[ruby-core:127015] [Ruby Bug#22418] Regex counted repetition disagrees with expanded equivalent pattern

8 Oct 2026


      Issue #22418 has been reported by robertmorelli (Robert Morelli).

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Bug #22418: Regex counted repetition disagrees with expanded equivalent pattern
https://bugs.ruby-lang.org/issues/22418

* Author: robertmorelli (Robert Morelli)
* Status: Open
* ruby -v: ruby 4.0.7 (2026-09-15 revision 229531a6cf) +PRISM [arm64-darwin27]
* Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN
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repro:
```ruby
/(?:u|\b){3}d/.match?("uud") # false
/(?:u|\b)(?:u|\b)(?:u|\b)d/.match?("uud")  # true
```
The counted repetition should be equivalent to duplicating the group but it is not.


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