sub bin2dec {
    return unpack("N", pack("B32", substr("0" x 32 . shift, -32)));
}

##</code><code>##

# Given a lsb-first bitstring, returns
# a 2s complement signed integer 
#
sub bin2signed
{
    my $bitstr = $_[0];
    my $is_negative = 0;

    if (substr($bitstr, -1, 1) eq "1")
    {
	    $bitstr =~ tr/10/01/;
	    $is_negative = 1;
    }

    my $result = 0;

    for (my $i = 0; $i < length($bitstr); ++$i)
    {
	    $result += substr($bitstr, $i, 1) * (2 ** $i);
    }

    if ($is_negative)
    {
	    $result += 1;
	    $result *= -1;
    }

    return $result;
}