Grammar    : Spacing Definition+ EndOfFile;
Definition : Identifier COLON Expression SEMI;
Expression : Sequence (BAR Sequence)*;
Sequence   : Prefix*;
Prefix     : (AND | NOT)? Suffix;
Suffix     : Primary (QUESTION | STAR | PLUS)?;
Primary    : Identifier !COLON
           | DOLLAR OPEN Expression CLOSE
           | DOLLAR Identifier OPEN Expression CLOSE
           | OPEN Expression CLOSE
           | Literal
           | Class
           | DOT;
Identifier : $(IdentStart IdentCont*) Spacing;
IdentStart : [a-zA-Z_];
IdentCont  : IdentStart
           | [0-9];
Literal    : ['] (!['] Char)* ['] Spacing
           | ["] (!["] Char)* ["] Spacing;
Class      : "[" (!"]" Range)* "]" Spacing;
Range      : Char "-" Char
           | Char;
Char       : "\\" [nrt'"\[\]\\]
           | "\\" [0-2] [0-7] [0-7]
           | "\\" [0-7] [0-7]?
           | !"\\" .;
COLON      : ":" Spacing;
SEMI       : ";" Spacing;
BAR        : "|" Spacing;
AND        : "&" Spacing;
NOT        : "!" Spacing;
QUESTION   : "?" Spacing;
STAR       : "*" Spacing;
PLUS       : "+" Spacing;
OPEN       : "(" Spacing;
CLOSE      : ")" Spacing;
DOT        : "." Spacing;
DOLLAR     : "$" Spacing;
Spacing    : $((Space | Comment)*);
Comment    : "#" (!EndOfLine .)* EndOfLine;
Space      : " "
           | "\t"
           | EndOfLine;
EndOfLine  : "\r\n"
           | "\n"
           | "\r";
EndOfFile  : !.;