#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
p       pcre2                                         use pcre2 regex engine
-       fatal="MESSAGE"                               print the given MESSAGE and exit
-       mgroup=N                                      a group in pattern determining the line number of tag
-       placeholder                                   don't put this tag to tags file.
-       scope=ACTION                                  use scope stack: ACTION = ref|push|pop|clear|set|replace|intervaltab
-       tenter=TABLE[,CONT]                           enter to given regext table (with specifying continuation)
-       tjump=TABLE                                   jump to another regext table(don't push the current table to state stack)
-       tleave                                        leave from the current regext table
-       tquit                                         stop the parsing with this parser
-       treset=TABLE                                  clear the state stack and jump to given regex table
-       warning="MESSAGE"                             print the given MESSAGE at WARNING level
-       _advanceTo=N[start|end]                       a group in pattern from where the next scan starts [0end]
-       _anonymous=PREFIX                             make an anonymous tag with PREFIX
-       _extra=EXTRA                                  record the tag only when the extra is enabled
-       _field=FIELD:VALUE                            record the matched string(VALUE) to parser own FIELD of the tag
-       _guest=PARSERSPEC,N0[start|end],N1[start|end] run guest parser on the area
-       _language=LANG                                make a foreign tag for LANG
-       _role=ROLE                                    set the given ROLE to the roles field
