my( @a, @b, @c );
( @a[0..19], @b[0..9], @c[0..3] ) = 
    unpack 'C20C10C4', 'abcdefghijklmnopqrst1234567890fred';

print "@a\n@b\n@c";
97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116
49 50 51 52 53 54 55 56 57 48
102 114 101 100