initial value,
you may prefix a <a href="#cap-cc">constant capture</a> to <code>patt</code>.)
For each subsequent capture
LPeg calls <code>func</code>
with this accumulator as the first argument and all values produced
by the capture as extra arguments;
the value returned by this call
becomes the new value for the accumulator.
The final value of the accumulator becomes the captured value.
</p>

<p>
As an example,
the following pattern matches a list of numbers separated
by commas and returns their addition: