private static function initExtnPatterns()
{
// One-character symbols that can be used to indicate an extension.
$singleExtnSymbolsForMatching = "xｘ#＃~～";
// For parsing, we are slightly more lenient in our interpretation than for matching. Here we
// allow a "comma" as a possible extension indicator. When matching, this is hardly ever used to
// indicate this.
$singleExtnSymbolsForParsing = "," . $singleExtnSymbolsForMatching;
self::$EXTN_PATTERNS_FOR_PARSING = self::createExtnPattern($singleExtnSymbolsForParsing);
self::$EXTN_PATTERNS_FOR_MATCHING = self::createExtnPattern($singleExtnSymbolsForMatching);
}
