Try some examples:
| urn:acct:(.*) | acct.php?resource=acct:$1 | WebFinger |
| urn:did:plc:(.*) | https://bsky.app/profile/did:plc:$1 | Bluesky |
| urn:doi:(.*) | https://doi.org/$1 | DOI |
| urn:hdl:(.*) | https://hdl.handle.net/$1 | Handle |
| urn:ietf:bcp:(\d*) | https://www.rfc-editor.org/info/bcp$1 | IETF Best Current Practice |
| urn:ietf:fyi:(\d*) | https://www.rfc-editor.org/info/fyi$1 | IETF FYI |
| urn:ietf:rfc:(\d*) | https://www.rfc-editor.org/info/rfc$1 | IETF RFC |
| urn:ietf:std:(\d*) | https://www.rfc-editor.org/info/std$1 | IETF Internet Standard |
| urn:ietf:id:(.*) | https://datatracker.ietf.org/doc/draft-$1/ | IETF Internet Draft |
| urn:isbn:(\d*) | https://isbnsearch.org/isbn/$1 | Book lookup |
| urn:lex:br:(.*) | https://www.lexml.gov.br/urn/urn:lex:br:$1 | Brazilian legislation |
| urn:xkcd:(\d*) | https://xkcd.com/$1/ | xkcd |