Changes
m
}}
</pre>
header1 will be shown if any of item_one, item_two, or item_three is defined, and won't be shown if none of those three parameters are defined.
The trick to this is that the "if" returns false only if there is nothing whatsoever in the conditional section, so only if all three of item_one, item_two and item_three are undefined will the if statement fail.