note tye The difference is that "b" is broken because it expects/produces the bits in the wrong order ["001" becomes chr(4)] while "B" is broken because short bit counts only deal with the highest bits ["001" becomes chr(32)]. (: [If multiple adjacent "b"/"B" formats could extract/set successive bits within a single byte, then this combination would be more reasonable.] So, if you are a normal person, you have to use "B" and pad your binary strings (in front, that is, to the left) to multiples of 8 characters (for [pack]) and only use multiples of 8 as lengths after the "B" (for [unpack]). It is called "ascending" bit order because it is assumed that you are reading the base-2 ASCII string (often confusingly called "binary" despite that term having way too many meanings in the context of [pack] and [unpack]) from left to right and, if you do that, the bits ascend in value from bit0=1, bit1=2, bit2=4, etc. While with "descending" bit order the leftmost "0" or "1" represents bit8=128 and the bit values descend from there. BTW, I find that the documentation for [pack]/[unpack] is rather ambiguous/confusing and it is very hard to make it completely unambiguous. I often resort to testing via "perl -de 0" when I have a question about some detail of these two functions. You might find that useful as well.         - [tye] (but my friends call me "Tye") 178576 178576