Legal values:
'beg-of-line - starts parsing at the beginning of a line, unless the
previous line ends with a backslash. Fast, but has
problems detecting multiline /* */ comments.
'beg-of-clause - starts parsing at the beginning of the current clause.
Slow, but copes better with /* */ comments."
Legal values:
'beg-of-line - starts parsing at the beginning of a line, unless the
previous line ends with a backslash. Fast, but has
problems detecting multiline /* */ comments.
'beg-of-clause - starts parsing at the beginning of the current clause.
Slow, but copes better with /* */ comments."