Bug #22418: Regex counted repetition disagrees with expanded equivalent pattern

• Status: Open
• Assignee: -
• Target version: -
• ruby -v: ruby 4.0.7 (2026-09-15 revision 229531a6cf) +PRISM [arm64-darwin27]
• Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN

[robertmorelli (Robert Morelli)]

repro:

/(?: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.