Regex: ^ Expression
Regex    ::= '^'? Expression
 no referencesExpression: Subexpression |
Expression
         ::= Subexpression ( '|' Subexpression )*
 referenced by: Group Regex Subexpression: SubexpressionItem
         ::= SubexpressionItem+
 referenced by: Expression SubexpressionItem: Match Group Anchor Backreference
         ::= Match
           | Group
           | Anchor
           | Backreference
 referenced by: Subexpression Group: ( ?: Expression ) Quantifier
Group    ::= '(' '?:'? Expression ')' Quantifier?
 referenced by: SubexpressionItem Match: MatchItem Quantifier referenced by: SubexpressionItem MatchItem: . MatchCharacterClass MatchCharacter
         ::= '.'
           | MatchCharacterClass
           | MatchCharacter
 referenced by: Match MatchCharacterClass: CharacterGroup CharacterClass CharacterClassFromUnicodeCategory
         ::= CharacterGroup
           | CharacterClass
           | CharacterClassFromUnicodeCategory
 referenced by: MatchItem MatchCharacter: Char
         ::= Char
 referenced by: MatchItem CharacterGroup: [ ^ CharacterGroupItem ]
         ::= '[' '^'? CharacterGroupItem+ ']'
 referenced by: MatchCharacterClass CharacterGroupItem: CharacterClass CharacterClassFromUnicodeCategory CharacterRange Char
         ::= CharacterClass
           | CharacterClassFromUnicodeCategory
           | CharacterRange
           | Char
 referenced by: CharacterGroup CharacterClass: \w \W \d \D
         ::= '\w'
           | '\W'
           | '\d'
           | '\D'
 referenced by: CharacterGroupItem MatchCharacterClass CharacterClassFromUnicodeCategory: \p{ UnicodeCategoryName }
         ::= '\p{' UnicodeCategoryName '}'
 referenced by: CharacterGroupItem MatchCharacterClass UnicodeCategoryName: Letters
         ::= Letters
 referenced by: CharacterClassFromUnicodeCategory CharacterRange: Char - Char
         ::= Char ( '-' Char )?
 referenced by: CharacterGroupItem Quantifier: QuantifierType ?
         ::= QuantifierType '?'?
 referenced by: Group Match QuantifierType: * + ? RangeQuantifier
         ::= '*'
           | '+'
           | '?'
           | RangeQuantifier
 referenced by: Quantifier RangeQuantifier: { RangeQuantifierLowerBound , RangeQuantifierUpperBound }
         ::= '{' RangeQuantifierLowerBound ( ',' RangeQuantifierUpperBound? )? '}'
 referenced by: QuantifierType RangeQuantifierLowerBound: Integer
         ::= Integer
 referenced by: RangeQuantifier RangeQuantifierUpperBound: Integer
         ::= Integer
 referenced by: RangeQuantifier Backreference: \ Integer
         ::= '\' Integer
 referenced by: SubexpressionItem Anchor: \b \B \A \z \Z \G $
Anchor   ::= '\b'
           | '\B'
           | '\A'
           | '\z'
           | '\Z'
           | '\G'
           | '$'
 referenced by: SubexpressionItem Integer: [0-9]
Integer  ::= [0-9]+
 referenced by: Backreference RangeQuantifierLowerBound RangeQuantifierUpperBound Letters: [a-z] [A-Z]
Letters  ::= [a-zA-Z]+
 referenced by: UnicodeCategoryName Char: [#x0009] [#x000A] [#x000D] [#x0020-#xD7FF] [#xE000-#xFFFD] [#x10000-#x10FFFF]
Char     ::= [#x0009#x000A#x000D#x0020-#xD7FF#xE000-#xFFFD#x10000-#x10FFFF]
 referenced by: CharacterGroupItem CharacterRange MatchCharacter   ... generated by Railroad Diagram Generator R R