This example taken from the manual:

// place at a particular offset to ensure loaded last $this->headScript()->offsetSetScript(100, '/js/myfuncs.js');

// use scriptaculous effects (append uses next index, 101) $this->headScript()->appendScript('/js/scriptaculous.js');

// but always have base prototype script load first: $this->headScript()->prependScript('/js/prototype.js');

Should be:

// place at a particular offset to ensure loaded last $this->headScript()->offsetSetFile(100, '/js/myfuncs.js');

// use scriptaculous effects (append uses next index, 101) $this->headScript()->appendFile('/js/scriptaculous.js');

// but always have base prototype script load first: $this->headScript()->prependFile('/js/prototype.js');

As the (append|prepend|offsetSet)Script() methods take JavaScript code as arguments and not an external file.