BEGIN {
    my $code= "";
    if(  pack("L",1) ne pack("N",1)  ) {
        $code= "''.reverse ";
    }
    eval "sub to_big_endian { ${code}pop }; 1"
        or die $@;
}
sub to_bin {
    my( $num )= @_;
    my( $sign, $exp, $mant )= unpack "A1A11A*", unpack "B*",
        to_big_endian pack"d",2*$num+1;
    $mant =~ s/10*$//;
    return "1".$mant;
}