You can remove the period and convert to lowercase:
lowercase(replace(Array.CurValue, ".", ""))
If there are many such characters that you need to remove, it may be easier to use a local variable:
set t to replace(Array.CurValue, ".", "")
set t to replace(t, ",", "")
set t to replace(t, ":", "")
set t to replace(t, "!", "")
set t to replace(t, "?", "")
set t to lowercase(trim(t))