This code checks if the variable <$error> is empty or not. If it is not empty, the contents are appended to a file called errorlog.
Example - Outputting text to the browser
This text will not be displayed because system output is set to off. However, text within an output tag will be displayed.
<while test="<$count> <= 10">
<if test="<$count.isinteger(even)> > 0">
<output><$count> is an even number<br></output>
2 is an even number
4 is an even number
6 is an even number
8 is an even number
10 is an even number
See the documentation for the SYSTEM tag for further examples.