Printing a variable only if it exisits

If a variable does not exist, then printing it produces an error. There are several methods of getting around this.

• We will start by setting $hasval to Has a Value, and not setting $noval
• Our test line will be: Testing ($noval) and ($hasval)

1. Suppress error messages (for part or all of document) with $OPT_verbose=-3 (not recommended!)
   e.g. $pushset $OPT_verbose=-3 $test $pop $OPT_verbose
2. $set $defaultval1=''l results in:
   Testing () and (Has a Value)
3. Using $if statement, e.g. using the pattern $if $xxx||$xxx||$endif results in:
   Has a Value
4. Inline conditional statement, e.g Testing ($iftrue $noval $noval '') and ($iftrue $hasval $hasval '') results in:
   Testing () and (Has a Value)
5. The preferred way using Testing ($noval.whenunset('')) and ($hasval.whenunset('')) results in:
   Testing () and (Has a Value)