Saxon

net.sf.saxon.style.PrincipalStylesheetModule contains a following code:

    public void registerImplicitModes(StyleElement element, RuleManager manager) {
        if (element instanceof XSLTemplate || element instanceof XSLApplyTemplates) {
            String modeAtt = element.getAttributeValue("mode");
            if (modeAtt != null) {
                String[] tokens = Whitespace.trim(modeAtt).split(" \t\n\r");
                for (String s : tokens) {

at the same time, please take a look at a signature of String.split() method:

    public String[] split(String regex) {
        return split(regex, 0);
    }

I doubt you meant to split string on such a separator.