$s = chr(0) x 40;;
vec( $s, $_, 32 ) = $_ for 0 .. 9;;
print unpack 'N*', $s;;
0 1 2 3 4 5 6 7 8 9

$s = pack 'N*', 0 .. 9;;
print vec( $s, $_, 32 ) for 0 .. 9;;
0
1
2
3
4
5
6
7
8
9

{ no warnings 'portable'; print vec( $s, $_, 64 ) for 0 .. 5 };;
1
8589934595
17179869189
25769803783
34359738377
0