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    my $rv = $handle->sysread($bufline, 4096);
    $line .= $bufline;
...
      $rv = $handle->sysread($bufline, 4096);
      $line .= $bufline unless !$rv;
    }

- While there are handles from which to read,
  - Wait for data to arrive.
...
  - While the buf has a full command,
    - Remove the command from the buf.
    - Process the command.

    my $bufline = "";
    my $rv = $handle->sysread($bufline, 4096);
    $line .= $bufline;

    my $rv = $handle->sysread($line, 4096, length($line));