#
  # NOTE: TBD
  #
  proc getIfNeededVersions { interp fileName } {
    set result [list]

    set oldPackageNames [interp eval $interp [list package names]]
    interp invokehidden $interp source $fileName; # [package ifneeded], etc.
    set newPackageNames [interp eval $interp [list package names]]

    foreach packageName $newPackageNames {
      if {[lsearch -exact $oldPackageNames $packageName] == -1} then {
        lappend result [list $packageName [lsort -decreasing \
            -command [list package vcompare] [interp eval \
            $interp [list package versions $packageName]]]]
      }
    }

    return $result
  }

  #
  # NOTE: This procedure attempts to extract a package version information
  #       from the specified file.  The fileName argument is the local file
  #       name to read.  This procedure may raise script errors.
  #
  proc extractVersionsFromFile { fileName } {
    switch -exact -- [file tail $fileName] {
      VERSION {
        return [list [string trim [readFile $fileName]]]
      }
      pkgIndex.eagle -
      pkgIndex.tcl {
        #
        # TODO: Evaluate the package index file in a new "safe"
        #       interpreter and obtain the newly added [package
        #       ifneeded] version(s)?
        #
        if {[catch {createInterp interp} error] == 0} then {
          set result [getIfNeededVersions $interp $fileName]
        } else {
          pkgLog [appendArgs \
              "could not create interp to extract versions: " \
              $error]

          set result [list]
        }

        if {[info exists interp]} then {
          catch {interp delete $interp}
          unset interp; # REDUNDANT
        }

        return $result
      }
    }
  }

  #
  # NOTE: This procedure checks if there is a higher version available of the
  #       specified package on the package file server.  The language argument

              [appendArgs $fileName .asc] \
              [appendArgs $downloadFileName .asc] $usePgp
        }

        set localFileName [file join $persistentDirectory $fileName]

        set compare [package vcompare \
            [lindex [extractVersionsFromFile $downloadFileName] 0] \
            [lindex [extractVersionsFromFile $localFileName] 0]]

        if {[isEagle]} then {
          file delete -recursive -- $temporaryDirectory
        } else {
          file delete -force -- $temporaryDirectory
        }