Debugging
HTML+ errors will point exactly at the tag or text where it happened so you know where the fix needs to happen.
On top of nice and specific error messages, there is a log tag which will log any value so you know under what context and what data the template is rendering.
<variable name="x" value="300"></variable>
<log value="x"></log>Log context and data
You may also log the current context by providing the $context string to the value attribute.
<log value="$current"></log>This $current value is only valid for log tag. Obviously, you may also print the whole data as well.
<log value="$data"></log>Log with label
Any text you put inside the log tag will be used as label.
<log value="$data.sample">sample data</log>