#       library path.
    #
    variable viaInstall; # DEFAULT: false

    if {![info exists viaInstall]} then {
      set viaInstall false
    }

    #
    # NOTE: The command to use when attempting to verify that Mono and its
    #       associated runtimes are installed locally.  Generally, this is
    #       not needed on Windows machines.
    #
    variable monoInstalledCommand; # DEFAULT: mono --version

    if {![info exists monoInstalledCommand]} then {
      set monoInstalledCommand {mono --version}
    }

    #
    # NOTE: The regular expression pattern used when attempting to verify
    #       that Mono and its associated runtimes are installed locally.
    #       Generally, this is not needed on Windows machines.
    #
    variable monoInstalledPattern; # DEFAULT: ^Mono JIT compiler version \d+\.

    if {![info exists monoInstalledPattern]} then {
      set monoInstalledPattern {^Mono JIT compiler version \d+\.}
    }
  }

  #
  # NOTE: This procedure modifies the URN variables used by the package
  #       downloader client so that one or more alternative (private?)
  #       backend file servers may be used.  The serverId argument must
  #       consist only of alphanumeric characters and it must begin with

    #       within the auto-path.
    #
    addToAutoPath $language $directory

    return true
  }

  #
  # NOTE: This procedure attempts to verify that an instance of Mono and its
  #       associated runtimes are installed locally.  There are no arguments.
  #       The return value is non-zero if Mono appears to be installed and
  #       available for use; otherwise, the return value is zero.
  #
  proc isMonoInstalled {} {
    variable monoInstalledCommand
    variable monoInstalledPattern

    if {[isEagle]} then {
      if {[catch {
        eval exec -success Success $monoInstalledCommand
      } result]} then {
        return false
      }
    } else {
      if {[catch {
        eval exec $monoInstalledCommand
      } result]} then {
        return false
      }
    }

    if {![info exists result] || \
        ![regexp -- $monoInstalledPattern $result]} then {
      return false
    }

    return true
  }

  #
  # NOTE: This procedure attempts to verify that some runtime is available to
  #       run CLR applications locally (e.g. the .NET Framework or Mono JIT).
  #       There are no arguments.  The return value is non-zero if it appears
  #       that CLR applications should be runnable locally; otherwise, the
  #       return value is zero.
  #
  proc canUseMsilPlatform {} {
    if {[isWindows]} then {
      #
      # HACK: Assume that all Windows operating systems have a compatible
      #       version of the .NET Framework is installed -AND- that it can
      #       be used to run any CLR application.
      #
      return true
    } else {
      #
      # HACK: On all other platforms, assume that Mono can be used to run
      #       any CLR application.
      #
      return [isMonoInstalled]
    }
  }

  #
  # NOTE: This procedure verifies the combination of language and version
  #       specified by the caller.  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 varName argument is the name

            $language $version $localPackageName $localFileNames $localUsePgp]

        if {[string length $varName] > 0} then {
          upvar 1 $varName newPlatform
        }

        #
        # NOTE: Check the current platform and the neutral platform, in that
        #       order, to see if that platform is supported by the package
        #       being saught.  If so, return that platform.
        # NOTE: First, check the current platform and the neutral platform,
        #       in that order, to see if that platform is supported by the
        #       package being saught.
        #
        set thesePlatforms [list [getPlatform] neutral]

        #
        # NOTE: Next, optionally, allow the "msil" platform to be checked.
        #       Currently, this is always applicable on Windows; however,
        #       on all other platforms this depends on having Mono and its
        #       associated runtimes installed locally.
        #
        if {[canUseMsilPlatform]} then {
          lappend thesePlatforms msil
        }

        #
        # NOTE: Check each applicable platform, in order, stopping when a
        #       supported platform is found for the package being saught.
        #
        foreach thisPlatform [list [getPlatform] msil neutral] {
        foreach thisPlatform $thesePlatforms {
          if {[lsearch -exact $platforms $thisPlatform] != -1} then {
            set newPlatform $thisPlatform
            return
          }
        }

        #
        # NOTE: If this point is reached, there are no supported platforms
        #       that are compatible with the current one for the specified
        #       package.
        #
        error "could not automatically detect platform"
      }
      msil -
      msil {
        #
        # NOTE: Forbid the "msil" platform if it is not available for use.
        #
        if {![canUseMsilPlatform]} then {
          error "platform \"msil\" does not appear to be supported"
        }
      }
      neutral -
      win32-arm -
      win32-x86 -
      win64-arm64 -
      win64-ia64 -
      win64-x64 {
        #