import Foundation
let pattern = #"(<(p|li)\b[^<>]*>[^<>\n]*)\b(Cat|Dog|Fish)\b([^<>\n]*<\/\2>)"#
let regex = try! NSRegularExpression(pattern: pattern, options: .anchorsMatchLines)
let testString = #"""
(1) <p> Cat test dfdsf</p>
(2) <p> Cat.</p>
(3) <p>Cat.</p>
(4) <p class="test">Cat</p>
(5) <li>Cat</li>
(6) <p>Catfgdggh</p>
(7) <div>Cat</div>
"""#
let stringRange = NSRange(location: 0, length: testString.utf16.count)
let substitutionString = #"$1lol$4"#
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