# Striim 3.9.4 / 3.9.5 documentation

##### Alternation ( | )

If you would like to specify several variations of an event sequence, use the alternation operator ( | ). In case there are equivalent variations in the alternation expression, the first (leftmost) variation will be matched first. For example, the following pattern matches A but not AA since it is equivalent to A:

PATTERN (A|AA|B|C)
DEFINE
A=streamA(sensor between 10 and 20),
AA=streamA(sensor between 10 and 20), -- it is same as A, and will never be matched
B=streamA(sensor > 20),
C=streamA(sensor < 10)