Search and install the plugin using the Extension Manager. Refer to Plugins on how to install plugins manually.

See also: http://karmin.ch/ebnf/

<ebnf> "EBNF defined in itself" {
syntax     = [ title ] "{" { production } "}" [ comment ].
production = identifier "=" expression ( "." | ";" ) .
expression = term { "|" term } .
term       = factor { factor } .
factor     = identifier
           | literal
           | "[" expression "]"
           | "(" expression ")"
           | "{" expression "}" .
identifier = character { character } .
title      = literal .
comment    = literal .
literal    = "'" character { character } "'"
           | '"' character { character } '"' .
}</ebnf>