my $code_file = '/tmp/myscript.cmds';
$SIG{HUP} = sub {
  unless ( -e $code_file ) {
    warn "Received HUP signal, but no command file.";
    return;
  }
  eval {
    require $code_file;
    unlink $code_file;
  };
  if ( ! $@ ) {
    warn "Caught HUP signal and processed command file";
  } else {
    warn "Caught HUP signal but unable to process commands: $@";
  }
};


##</code><code>##

> echo "$foo = 27" >> /tmp/myscript.cmds
> killall -HUP perl