LANGTAG top-level property
144s 	LANGTAG 	::= 	'@' a-zA-Z+ ('-' a-zA-Z0-9+)*
Implementation
final LANGTAG = pattern('@') &
    pattern('a-zA-Z').plus() &
    (pattern('-') & pattern('a-zA-Z0-9').plus()).star();144s 	LANGTAG 	::= 	'@' a-zA-Z+ ('-' a-zA-Z0-9+)*
final LANGTAG = pattern('@') &
    pattern('a-zA-Z').plus() &
    (pattern('-') & pattern('a-zA-Z0-9').plus()).star();