Quote the docs:

Because infinite loops requiring a HUP or KILL signal to terminate are generally in poor taste, the HTTP::Daemon side of this sets up a localized signal handler which causes an exit when triggered. By default, this is attached to the INT signal. If the Net::Server module is being used instead, it provides its own signal management.

So press Ctrl-C, or use your system's kill command to send SIGINT to the process.

If the Net::Server module is being used instead, it provides its own signal management.

Reading Net::Server's docs, we learn that it listens for the INT, TERM and QUIT signals. So press Ctrl-C, or use your system's kill command to send one of those signals to the process.