function regexp() {
	var re = '/';
	if ( ch === '/' ) {
		goNext( '/' );
		if ( ch === '/' ) {
			goNext( '/' );
			return new RegExp();
		}
		while ( ch ) {
			re += ch;
			if ( ch === '/' ) {
				goNext( '/' );
				while ( ch === 'i' || ch === 'g' || ch === 'm' ) {
					re += ch;
					goNext();
				}
				return reFromString( re );
			}
			goNext();
		}
	}
}
Parses a regular expression.

@private
@returns {RegExp} parsed regular expression