re = /IT1[^@]*EA[^@]*@(?:(?!@IT1).)*REF[^@]*BAR[^@]*@/m
str = 'IT1*1*EA*VN*ABC@SAC*X*500@REF*ZZ*OK@IT1*1*CS*VN*ABC@SAC*X*500@REF*ZZ*BAR@IT1*1*EA*VN*ABC@SAC*X*500@REF*ZZ*BAR@IT1*1*EA*VN*ABC@SAC*X*500@REF*ZZ*OK@'
# Print the match result
str.scan(re) do |match|
puts match.to_s
end
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Ruby, please visit: http://ruby-doc.org/core-2.2.0/Regexp.html