I switched this to `/^ENC:?(\w*)\[(.*)\]$/` to match the `\w` in the original regex.  This means the key can only contain alphanumerics or underscores.  I'd be willing to consider other characters, but it should be in a separate PR if it isn't a requirement for 1.8.7 support.  Also need to be careful about supporting `[` in key names, because it would make the distinction between key and value confusing.