Ruby

From irb, when calling String#match?

pattern = /([\s]*ABC)$/i # or /(\s*ABC)/i

p "1ABC".match?(pattern) # => true
p "12ABC".match?(pattern) # => true
p "123ABC".match?(pattern) # => true
p "1231ABC".match?(pattern) # => true
p "12312ABC".match?(pattern) # => false
p "123123ABC".match?(pattern) # => false
p "1231231ABC".match?(pattern) # => true
p "12312312ABC".match?(pattern) # => true
p "123123123ABC".match?(pattern) # => false
p "1231231231ABC".match?(pattern) # => false
p "12312312312ABC".match?(pattern) # => true
p "123123123123ABC".match?(pattern) # => true
p "1231231231231ABC".match?(pattern) # => false

With ruby 3.2.2 (2023-03-30 revision e51014f9c0) [x86_64-darwin22] and earlier versions (2.7.8 to 3.2.2) return value is always true

Update: the problem seems to be somehow related to the /i option, as all the above examples work correctly with /([\s]*ABC)$/