Appendix B. HTTP Status Codes

Contents:

100s: Informational
200s: Successful
300s: Redirection
400s: Client Errors
500s: Server Errors

You can find a detailed explanation of each status code in RFC 2616 (Hypertext Transfer Protocol—HTTP/1.1) at http://www.rfc-editor.org.

B.1. 100s: Informational

If an LWP request gets either of these rarely used codes, $response->is_info will be true. For all other status codes, $response->is_info will be false. 

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101 Switching Protocols