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146 ” PCRE Extension
Alternation
It’s possible to check for multiple expressions simultaneously in a single pattern, also
called alternation, using the pipe meta-character |.
N o t e that the ˆ and $ are not implicitly applied to all expressions in an alternation;
they must be used explicitly for each expression.
The first example returns 1 because ’abar’ contains ’bar’ since , ˆ is not applied to
that expression in the pattern. The second example does apply ˆ to ’bar’ and, since
’abar’ begins with neither ’foo’ nor ’bar’ it returns , 0.
R e p e t i t i o n and Quantifiers
P a r t of a pattern may or may not be present, or may be repeated a number of times.
This is referred to as repetition and involves using meta-characters collectively referred
to as quantifiers.