#LETTER NAME                    DESCRIPTION
b       basic                   interpreted as a Posix basic regular expression.
e       extend                  interpreted as a Posix extended regular expression (default)
i       icase                   applied in a case-insensitive manner
-       mgroup=N                a group in pattern determining the line number of tag
-       _advanceTo=N[start|end] a group in pattern from where the next scan starts [0end]
-       _extra=EXTRA            record the tag only when the extra is enabled
-       _field=FIELD:VALUE      record the matched string(VALUE) to FIELD of the tag
