print "am in $0\n";

{
  local $/;

  seek DATA, 0, 0;

  (my $data = <DATA>) =~ s/\bexec\b.*\n//;

  open(ME, ">$0") or die("ack - $!");

  print ME qq[print "am in new \$0\\n";\n], $data;

  close ME;

}

exec "perl $0";

__DATA__