BEGIN {
    if (@ARGV && $ARGV[0] eq '--fixed') {
        shift(@ARGV);
    } else {
        $ENV{PATH} = join ':', '/mypath/perl/bin', $ENV{PATH};
        delete $ENV{PERL5LIB};
        exec '/mypath/perl/bin/perl', $0, '--fixed', @ARGV;
        die ...;
    }
}