Question: How to assign a long list by using Arrays?

I have the following command.

with(StringTools);
message := `Kajian ini mempunyai tiga objektif pertama seperti yang ditunjukkan dalam bahagian 1.11. Objektif tersebut harus`;

m := convert(message, bytes);

block := map(convert, m, binary);
block := map2(nprintf, "%08d", block);
block := map(proc (t) options operator, arrow; [seq(parse(convert(t, string)[i]), i = 1 .. length(convert(t, string)))] end proc, block);

block := [[0, 1, 0, 0, 1, 0, 1, 1], [0, 1, 1, 0, 0, 0, 0, 1], [0, 1, 1, 0, 1, 0, 1, 0], [0, 1, 1, 0, 1, 0, 0, 1], ........]

with(Bits);
for i to l do
for j from 3 to 7 do
block[i][j] := 1-block[i][j];  //used to flip bit in between 3rd to 7th bit in a block
end do;
c_block[i] := block[i];
end do;
c_block1 := [seq(c_block[i], i = 1 .. l)];

Error, assigning to a long list, please use Arrays

May i know how to solve this problem? I need to change some bit in a list but receive error when there is more than 100 elements in a list. Thank you.