private String determineQuote(String candidate) {
        if (isIpAddress(candidate)) {
            /*
             * If the IP address has a mask (for example 1.2.3/8), then it seems the convention is to just
             * to chop off the /slash part and replace it with .*
             */
            IPAddressString ipString = new IPAddressString(candidate);
            if (ipString.isPrefixed()) {
                // Snip off the prefix segment replace it with .*
                String withoutPrefix = StringUtils.removeEnd(candidate, "/" + ipString.getNetworkPrefixLength());
                LOGGER.debug("Found prefixed IP address {0} -> {1}", ipString, withoutPrefix + ".*");
                return Pattern.quote(withoutPrefix) + ".*";

            }
        }
        return Pattern.quote(candidate);
    }
Seems it is common to support wildcards at only the start or end of the entry, so we'll do that for
now. If anyone wants wildcard support elsewhere they can ask for it.

We use Pattern.quote to make the rest of the string 'safe'.
gateway/platforms/vertx3/vertx3/src/main/java/io/apiman/gateway/platforms/vertx3/engine/proxy/JavaSysPropsProxySettings.java