static boolean isAlias(String s) {
        Validate.notNull(s);
        return s.startsWith("$") && pattern.matcher(s).matches();
    }
Checks whether a given String is a valid OPM Expression, this means
either an Address or an alias ${xxx}.
plc4j/tools/opm/src/main/java/org/apache/plc4x/java/opm/OpmUtils.java