title: Tcl access array key from a value declare in another file
body: <p>I am working on main script that is souring  a file eg
  <code>foo.tcl</code>
  In <code>foo.tcl</code> , we have some <code>array</code> variable declare
    eg</p>
  
  <pre><code>   array set foo {
         "john" "doe"
         "alpha" "beta"
     }
  </code></pre>
  
  <p>In the main script we are trying to access the value using the key of array</p>
  
  <pre><code>source foo.tcl
  set key "john"
  puts ${::foo($key)} ;# can't read "::foo($key)": no such element in array
  puts ${::foo(john)} ;# not giving error
  </code></pre>
  
  <p>How to access pass the dynamic key to the array?</p>