How to separate or split strings that are written in one word?

You have to use the letter l (small L) and not the number 1.
The same applies to your choice of the pipe symbol.
This regular expression works as described
$regexp('TagsLikeThese ',(\w|,)(?=\u),$1 $2)
and this one also:
$regexp('TagsLikeThese ',(\l)(\u),$1 $2)