The parser documents what it has found by counting all caller-callee pairs and rendering this as a directed graph. For long running parses the counts so far are reported frequently throughout the run.
Exploratory parsing lets you divide string matches into those you expect and others. See this example developed step by step. post 
The output format is that used by dot, a part of the graphviz suit of visualization tools. The dot format can be rendered in svg with hyperlinks. We make the counts on arcs between parse rule names link to a list of matches saved by the Regrade Tally logic.
By convention rules that permissively match unexpected characters are given names prefixed with 'other'. These are colored gray in the visualization.