title: Tcl variable existence
body: <p>I need to check if </p>
  
  <pre><code>get_property PWROPT_WRITE_MODE_CHANGE_A $obj
  </code></pre>
  
  <p>is set or not. get_property will return me a string if property/attribute PWROPT_WRITE_MODE_CHANGE_A is set on object $obj otherwise return 0.
  If I do info exists as below, it will always return me 0 because info exists will check on the return value of get_property PWROPT_WRITE_MODE_CHANGE_A $obj.</p>
  
  <pre><code>if { [ info exists [get_property PWROPT_WRITE_MODE_CHANGE_A $var] ] } {
  
  }
  </code></pre>
  
  <p>Any pointers?</p>