How to search "error." pattern with LOG

Hello,

I am trying to monitor a log file in order to be alerted when the string 
"error." appears.

For instance :

error.grammar
error.noressource

... should send an alert

but "error " (with a space after) should not.

I tried to put in hobbit-clients.cfg :

LOG     /tmp/log error. COLOR=yellow
==> does not work

LOG     /tmp/log %(?-i)error. COLOR=yellow
==> works but match with error (without the .)

Does anyone can help me to find the correct regexp please ?

Thank you,

Vincent