g = [1, 2, nil, nil, nil, 3, nil, nil, nil, nil]
a = [55, 45, 56]
b = [100, 200, 300, 400]

g = [1, 2, 55, 45, 56, 3, 100, 200, 300, 400]

g = [1,2,nil,nil,nil,3,nil,nil,nil,nil]
a = [55,45,56]
b = [100,200,300,400]

g.fill(2, a.size) { |i| a[i] }
#=> [1,2,55,45,56,3,nil,nil,nil,nil]
g.fill(6, b.size) { |i| b[i] }
#=> [1,2,55,45,56,3,100,200,300,400]

g.insert(6, *b); // inserts b into 6 index
g.insert(2, *a); // inserts a into 2 index
g.compact! // removes the nil elements

foo[insertion_point, length] = values

g = [1,2,nil,nil,nil,3,nil,nil,nil,nil]
a = [55,45,56]
b = [100,200,300,400]

g[2, a.size] = a
g #=> [1, 2, 55, 45, 56, 3, nil, nil, nil, nil]
g[6, b.size] = b
g #=> [1, 2, 55, 45, 56, 3, 100, 200, 300, 400]