import Foundation
let pattern = #"<ref>(?:(?!<\/ref>).)*example\.com.*?<\/ref>"#
let regex = try! NSRegularExpression(pattern: pattern, options: .anchorsMatchLines)
let testString = #"<ref>{{cite web|title=Foo|url=https://zzz.com/foo}}</ref> blah-blah <ref>{{cite web|title=Bar|url=https://example.com/bar}}</ref> some more blah <ref>{{cite web|title=Foo|url=https://pqr.com/foo}}</ref>"#
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