In short, they have different priorities. The priority of
oris even lower than
Forgetting this can easily cause problems.
from = "some random string" to = "AAA" from[/random/] = to or "DEFAULT" # actually means (from[/random/] = to) or "DEFAULT" # and never replace matched part with "DEFAULT" # one should use from[/random/] = to || "DEFAULT"
Reference: this SO answer