In a POSIX environment, causing a long-running process such as a daemon to stop and load the latest configuration information is often associated with the HUP signal.

Perhaps you could put in a signal handler that would allow you to eval some new code in, and then continue, along the following (untested) lines:

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: $@";
  }
};
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While your script is running interactively, you can use another session to write commands to this file and HUP your running Perl process.

> echo "$foo = 27" >> /tmp/myscript.cmds
> killall -HUP perl
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A major caveat: signal handlers are notoriously finicky and idiosyncratic, so this approach might not be particularly reliable or portable.