import Foundation
let pattern = #"\d+\K\."#
let regex = try! NSRegularExpression(pattern: pattern, options: .anchorsMatchLines)
let testString = #"""
1. Wallbaum, H., S. Krank,
3. Levinson, H.S., Highways, people,
4. Mercier, J., Equity, social justice,
225. Lemp, J.D., et al.,
17. Chi, G. and B. Stone,
"""#
let stringRange = NSRange(location: 0, length: testString.utf16.count)
let substitutionString = #"|"#
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