#       a package index file.  The language argument must be one of the
  #       literal strings "eagle", "tcl", or "client".  The fileNames argument
  #       must be the list of file names to be downloaded.  The package name,
  #       if one can be detected, is returned; otherwise, an empty string will
  #       be returned.
  #
  proc guessPackageNameFromFileNames { language fileNames } {
    set packageIndexFileName [getPackageIndexFileName $language]
    set packageIndexFileNameOnly [getPackageIndexFileName $language]

    if {[string length $packageIndexFileName] > 0} then {
    if {[string length $packageIndexFileNameOnly] > 0} then {
      foreach fileName $fileNames {
        set fileNameOnly [file tail $fileName]

        if {$fileNameOnly eq $packageIndexFileName} then {
        if {$fileNameOnly eq $packageIndexFileNameOnly} then {
          set directory [file dirname $fileName]

          if {[string length $directory] > 0} then {
            return [file tail $directory]
          }
        }
      }

        set downloadDirectories [list $persistentDirectory]
      } else {
        #
        # NOTE: Check each unique download directory for a package index
        #       file.  If a directory has a package index for the target
        #       language, add to the auto-path for the target language.
        #
        set packageIndexFileName [getPackageIndexFileName $language]
        set packageIndexFileNameOnly [getPackageIndexFileName $language]

        if {[string length $packageIndexFileName] > 0} then {
        if {[string length $packageIndexFileNameOnly] > 0} then {
          foreach downloadDirectory $downloadDirectories {
            if {[file exists [file join \
                $downloadDirectory $packageIndexFileName]]} then {
                $downloadDirectory $packageIndexFileNameOnly]]} then {
              addToAutoPath $language $downloadDirectory
            }
          }
        }
      }
    }

    #
    # NOTE: Initially, no temporary package directories have been added
    #       to the auto-path.
    #
    set result [list]; set packageNames [list]

    #
    # NOTE: What is the package index file name for this language?  Each
    #       candidate temporary package directory will be checked to see
    #       if it contains this file; otherwise, it will not be added to
    #       the auto-path.
    #
    set packageIndexFileNameOnly [getPackageIndexFileName $language]

    #
    # HACK: Obtain the list of candidate temporary package directories
    #       that may need to be added to the auto-path.  The prefix we
    #       use here is considered "well-known" by this package.
    #
    set directories(1) [glob -nocomplain -types {d} \
        [file join $temporaryRootDirectory pkgd_lib_*]]

    foreach directory(1) $directories(1) {
      set directories(2) [glob -nocomplain -types {d} \
          [file join $directory(1) *]]

      foreach directory(2) $directories(2) {
        set directoryNameOnly(2) [file tail $directory(2)]
        set packageName $directoryNameOnly(2); # HACK: Well-known.

        if {[lsearch -exact $packageNames $packageName] == -1} then {
          if {[string length $pattern] == 0 || \
              [string match $pattern $directoryNameOnly(2)]} then {
            if {[string length $packageIndexFileNameOnly] == 0 || \
                [file exists [file join $directory(2) \
                    $packageIndexFileNameOnly]]} then {
            if {[maybeAddToAutoPath $language $directory(2)]} then {
              lappend packageNames $directoryNameOnly(2)
              lappend result $directory(2)
              if {[maybeAddToAutoPath $language $directory(2)]} then {
                lappend packageNames $directoryNameOnly(2)
                lappend result $directory(2)

              if {$verboseTemporaryDirectory} then {
                pkgLog [appendArgs \
                    "added temporary package directory named \"" \
                    $directory(2) "\" to auto-path..."]
                if {$verboseTemporaryDirectory} then {
                  pkgLog [appendArgs \
                      "added temporary package directory named \"" \
                      $directory(2) "\" to auto-path..."]
                }
              }
            }
          }
        }
      }
    }