Overwrite slices in l according to pairs.
Return new list.
abjad> l = range(10)
listtools.overwrite_slices_at(l, [(0, 3), (5, 3)])
[0, 0, 0, 3, 4, 5, 5, 5, 8, 9]
abjad> l = range(10)
listtools.overwrite_slices_at(l, [(0, 99)])
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
Todo
Implement optional period keyword.
Todo
Read anchor_index and length values cyclically.