error "unsupported language"
    }
  }

  #
  # NOTE: This procedure verifies the platform specified by the caller.  The
  #       platform argument must be an empty string -OR- one of the literal
  #       strings "win32-arm", "win32-x86", "win64-arm64", "win64-ia64", or
  #       "win64-x64".  An empty string means that the associated entity does
  #       not require a specific platform.  Upon failure, a script error will
  #       be raised.  The return value is undefined.
  #       strings "neutral", "win32-arm", "win32-x86", "win64-arm64",
  #       "win64-ia64", or "win64-x64".  An empty string means that the
  #       associated entity does not require a specific platform.  Upon
  #       failure, a script error will be raised.  The return value is
  #       undefined.
  #
  proc verifyPlatform { platform varName } {
    switch -exact -- $platform {
      "" {
        #
        # NOTE: This platform name is supported; however, the name needs
        #       to be normalized to "neutral".
        #
        # TODO: In the future, the empty string may mean "automatically
        #       detect" the necessary platform instead of always being
        #       mapped to "neutral".
        #
        if {[string length $varName] > 0} then {
          upvar 1 $varName newPlatform; set newPlatform neutral
        }
      }
      neutral -
      win32-arm -
      win32-x86 -
      win64-arm64 -
      win64-ia64 -
      win64-x64 {
        #
        # NOTE: This platform name is supported verbatim, do nothing.

  #
  # NOTE: This procedure checks if there is a higher version available of the
  #       specified package on the package file server.  The language argument
  #       must be one of the literal strings "eagle", "tcl", or "client".  The
  #       version argument must be one of the literal strings "8.4", "8.5", or
  #       "8.6" when the language is "tcl" -OR- the literal string "1.0" when
  #       the language is either "eagle" or "client".  The platform argument
  #       must be an empty string -OR- one of the literal strings "win32-arm",
  #       "win32-x86", "win64-arm64", "win64-ia64", or "win64-x64".  An empty
  #       string means that the associated package does not require a specific
  #       platform.  The packageName argument is a directory name relative to
  #       the language and version-specific directory on the package file
  #       server and may be an empty string.  The usePgp argument should be
  #       non-zero when an OpenPGP signature file needs to be downloaded and
  #       verified for the downloaded file.
  #       must be an empty string -OR- one of the literal strings "neutral",
  #       "win32-arm", "win32-x86", "win64-arm64", "win64-ia64", or
  #       "win64-x64".  An empty string means that the associated package
  #       does not require a specific platform.  The packageName argument is
  #       a directory name relative to the language and version-specific
  #       directory on the package file server and may be an empty string.
  #       The usePgp argument should be non-zero when an OpenPGP signature
  #       file needs to be downloaded and verified for the downloaded file.
  #
  # <public>
  proc checkForHigherVersion { language version platform packageName usePgp } {
    variable clientDirectory
    variable persistentRootDirectory
    variable temporaryRootDirectory

  #       downloaded, this procedure assumes the corresponding data file was
  #       already downloaded (i.e. since OpenPGP needs both to perform the
  #       signature checks).  The language argument must be one of the
  #       literal strings "eagle", "tcl", or "client".  The version argument
  #       must be one of the literal strings "8.4", "8.5", or "8.6" when the
  #       language is "tcl" -OR- the literal string "1.0" when the language
  #       is either "eagle" or "client".  The platform argument must be an
  #       empty string -OR- one of the literal strings "win32-arm",
  #       empty string -OR- one of the literal strings "neutral", "win32-arm",
  #       "win32-x86", "win64-arm64", "win64-ia64", or "win64-x64".  An empty
  #       string means that the associated package does not require a specific
  #       platform.  The fileName argument is a file name relative to the
  #       language and version-specific directory on the package file server.
  #       The localFileName argument is the file name where the downloaded
  #       file should be written.  The usePgp argument should be non-zero when
  #       an OpenPGP signature file needs to be downloaded and verified for

  # NOTE: This procedure attempts to download a list of files, optionally
  #       persistening them for subsequent uses by the target language.
  #       The language argument must be one of the literal strings "eagle",
  #       "tcl", or "client".  The version argument must be one of the
  #       literal strings "8.4", "8.5", or "8.6" when the language is "tcl"
  #       -OR- the literal string "1.0" when the language is either "eagle"
  #       or "client".  The platform argument must be an empty string -OR-
  #       one of the literal strings "win32-arm", "win32-x86", "win64-arm64",
  #       "win64-ia64", or "win64-x64".  An empty string means that the
  #       associated package does not require a specific platform.  The
  #       fileNames argument must be a well-formed list of file names to
  #       one of the literal strings "neutral", "win32-arm", "win32-x86",
  #       "win64-arm64", "win64-ia64", or "win64-x64".  An empty string means
  #       that the associated package does not require a specific platform.
  #       The fileNames argument must be a well-formed list of file names to
  #       download, each one relative to the language and version-specific
  #       directory on the package file server.  The options argument must
  #       be a dictionary of name/value pairs.  The -persistent option should
  #       be non-zero if the downloaded files should be saved to permanent
  #       storage for subsequent use.  The -usePgp option should be non-zero
  #       when an OpenPGP signature file needs to be downloaded and verified
  #       for each downloaded file.  The -useAutoPath option should be