import Foundation
let pattern = #"^.+ (\w+) 3160 211 50 0(\w+)\d{3} .+$"#
let regex = try! NSRegularExpression(pattern: pattern, options: [.anchorsMatchLines, .caseInsensitive])
let testString = #"""
RD32 MK12001 3160 211 50 02100123001 SERVER LOCAL - STREET
RD32 MK13103 3160 211 50 02100124001 SERVER LOCAL - CITY
RD32 J4834-00009-92051 MRDOOP 3160 211 50 021005237001 SERVER GIVEN NAME
RD32 B5509-00000-00522 JPPK 3160 211 50 02123133001 SERVER GIVEN NAME
"""#
let stringRange = NSRange(location: 0, length: testString.utf16.count)
let substitutionString = #"$1 C$2"#
let result = regex.stringByReplacingMatches(in: testString, range: stringRange, withTemplate: substitutionString)
print(result)
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 Swift 5.2, please visit: https://developer.apple.com/documentation/foundation/nsregularexpression