import Foundation
let pattern = #"<\?xml version="1\.0" encoding="UTF-8"\?>\s*<\s*([^\s]*)(?:.|\s)*<\/\s*\1\s*>"#
let regex = try! NSRegularExpression(pattern: pattern, options: .anchorsMatchLines)
let testString = #"""
--------------------------3cbec9ce8f05
Content-Disposition: form-data; name="owServerData"; filename="details.xml"
Content-Type: text/plain
<?xml version="1.0" encoding="UTF-8"?>
<Devices-Detail-Response xmlns="http://www.example.com"
<device>a</device>
<info>abc</info>
<test1><u>123</u><v>456</v><z/></test1>
</Devices-Detail-Response>
------------------------------3cbec9ce8f05--
"""#
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