The problem with N versus V is that it swaps byte-order not bit-order. ie.

printf '%08x', unpack 'N', $Vpacked
printf '%08x', unpack 'N', $Npacked
printf '%08x', unpack 'V', $Vpacked
printf '%08x', unpack 'V', $Npacked

04030201
01020304
01020304
04030201
[download]

So, depending on you local endianess and that of the source, and whether you want the bits in l-r or r-l order, there are four possible permutations to consider.

 $num = 0x01020304;

 $Npacked = pack 'N', $num;
 $Vpacked = pack 'V', $num;

 print map{ vec $Vpacked,      $_, 1 } 0 .. 31
 print map{ vec $Npacked,      $_, 1 } 0 .. 31
 print map{ vec $Vpacked, 31 - $_, 1 } 0 .. 31
 print map{ vec $Npacked, 31 - $_, 1 } 0 .. 31
 
00100000 11000000 01000000 10000000
10000000 01000000 11000000 00100000
00000001 00000010 00000011 00000100
00000100 00000011 00000010 00000001
[download]

Hopefully one of these will be what your looking for...unless you source is one of the 6-bit byte/3-byte word machines in which case all bets are off:)

Note: I broke up the output into 8's manually. Couldn't think of a clean way of doing it without obscuring the code.