We needed to enable metric "Log File Pattern Matched Line Count" from OEM.
We were looking for java.lang.OutOfMemory string within our weblogic log file.
As first time user, I went ahead and added the string name and really did not care to check the "Ignore Pattern in Perl" that had "%" by default.
This was telling the EM to ignore virtually everything and no wonder we did not receive alerts.
The right to look for a string "java.lang.OutOfMemoryError" was: