s = "GE.O A SSSS !@# world E A A D a9e DX.X you"
r = /(?-i)(?<=\s|^)[A-Z]{1,4}(\.[A-Z]{1,2})?(?=\s|$)/
if s =~ r
matches = s.to_enum(:scan, r).map { Regexp.last_match }
puts matches
puts matches.length
puts matches.kind_of?(Array)
puts matches.include?("A")
end
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