When a set of patterns is not working the parser will either produce the wrong
output, loop indefinitely, or crash. You can turn on debugging with the
-d1 and -d2 flags to see what the DFA (Determinate Finite Automata,
which isn't quite true)
representation of your input patterns is. The -d1 option shows the
various arrays defining the DFA, and the -d2 options shows a trace of
the build of the main state arrays. It is beyond the scope of this
document to describe the contents and structure of these arrays.
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