translate English to French: For example, ((?i)rah)\s+\1 matches "rah rah" and "RAH RAH", but not "RAH rah", even though the original capturing subpattern is matched case-insensitively (caselessly).
Par exemple, ((?i)rah)\s+\1 trouve "rah rah" et "RAH RAH", mais pas "RAH rah", même si le sous-masque capturant initial ne tenait pas compte de la casse.