Internal Error

can't read "uri": no such variable
    while executing
"subst $body"
    (class "::httpd::document.cuneiform" method "subst" line 2)
    invoked from within
"my  subst [dict get $data body]"
    (class "::httpd::content.cuneiform" method "content" line 8)
    invoked from within
"my content"