END {
    open FH, "< $0" or warn "Failed to preserve state... couldn't open '$0', $!" and exit(1);
    local $/;
    $_ = <FH>;
    s/my \$var=$oldvalue/my \$var=$var/m;
    open FH, "> $0" or warn "Failed to preserve state... couldn't write to '$0', $!" and exit(1);
    print FH $_;
    close $file;
}