When I run your code on a linux box, the child process catches a SIGPIPE after telnet exits *and* it tries to subsequently write to the socket:

broken pipe at ././test-server2 line 50
        main::SELFREAP('PIPE') called at ././test-server2 line 85
        main::__ANON__() called at ././test-server2 line 121
        main::spawn('CODE(0x80cdb14)') called at ././test-server2 line
+ 96
broken pipe at ././test-server2 line 50
        main::SELFREAP('PIPE') called at ././test-server2 line 0
././test-server2 9192: reaped 9761 with exit 7424 at Wed Apr  5 12:23:
+32 2000
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What platform are you running on. Trying to write to a closed socket should definitely generate a SIGPIPE.