import Foundation
let pattern = #"\s*\{\{source\|(?>[^{}]|(\{\{(?:[^{}]++|(?1))*}}))*}}\s*"#
let regex = try! NSRegularExpression(pattern: pattern, options: .anchorsMatchLines)
let testString = ##"""
# Test is a cool word {{source|{{nom w pc|Chantal|Bouchard}}, ''La langue et le nombril'', Presses de l'Université de Montréal (PUM), 2020, p. 174}}.
# Test is a cool word {{source|Nicolas|Daniel, Presses de l'Université de Montréal 4}}
"""##
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