# NOTE: This procedure returns non-zero if the specified package appears to
  #       be present.  The package argument is the name of the package being
  #       sought, it cannot be an empty string.  The version argument must be
  #       a specific version -OR- a package specification that conforms to TIP
  #       #268.
  #
  proc isPackagePresent { package version } {
    variable verboseUnknownResult

    set command [list package present $package]
    if {[string length $version] > 0} then {lappend command $version}

    if {[set code [catch $command result]] == 0} then {
      if {$verboseUnknownResult} then {
      pkgLog [appendArgs \
          "package \"" [formatPackageName $package $version] \
          "\" was loaded: " [formatResult $code $result]]
        pkgLog [appendArgs \
            "package \"" [formatPackageName $package $version] \
            "\" was loaded: " [formatResult $code $result]]
      }

      return true
    } else {
      if {$verboseUnknownResult} then {
      pkgLog [appendArgs \
          "package \"" [formatPackageName $package $version] \
          "\" was not loaded: " [formatResult $code $result]]
        pkgLog [appendArgs \
            "package \"" [formatPackageName $package $version] \
            "\" was not loaded: " [formatResult $code $result]]
      }

      return false
    }
  }

  #
  # NOTE: This procedure returns non-zero if the specified package appears to
  #       be available.  The package argument is the name of the package being
  #       sought, it cannot be an empty string.  The version argument must be
  #       a specific version -OR- a package specification that conforms to TIP
  #       #268.
  #
  proc isPackageAvailable { package version } {
    variable verboseUnknownResult

    set packageVersions [package versions $package]

    if {[llength $packageVersions] == 0} then {
      if {$verboseUnknownResult} then {
      pkgLog [appendArgs \
          "package \"" [formatPackageName $package $version] \
          "\" is not available: no versions"]
        pkgLog [appendArgs \
            "package \"" [formatPackageName $package $version] \
            "\" is not available: no versions"]
      }

      return false
    }

    if {[string length $version] == 0} then {
      if {$verboseUnknownResult} then {
      pkgLog [appendArgs \
          "package \"" [formatPackageName $package $version] \
          "\" is available: no version"]
        pkgLog [appendArgs \
            "package \"" [formatPackageName $package $version] \
            "\" is available: no version"]
      }

      return true
    }

    foreach packageVersion $packageVersions {
      if {[package vsatisfies $packageVersion $version]} then {
        if {$verboseUnknownResult} then {
        pkgLog [appendArgs \
            "package \"" [formatPackageName $package $version] \
            "\" is available: version satisfied by \"" \
            [formatPackageName $package $packageVersion] \"]
          pkgLog [appendArgs \
              "package \"" [formatPackageName $package $version] \
              "\" is available: version satisfied by \"" \
              [formatPackageName $package $packageVersion] \"]
        }

        return true
      }
    }

    if {$verboseUnknownResult} then {
    pkgLog [appendArgs \
        "package \"" [formatPackageName $package $version] \
        "\" is not available: version not satisfied"]
      pkgLog [appendArgs \
          "package \"" [formatPackageName $package $version] \
          "\" is not available: version not satisfied"]
    }

    return false
  }

  #
  # NOTE: This procedure returns non-zero if the specified package can be
  #       downloaded, i.e. because it is not required for the downloading

      pkgLog [appendArgs \
          "initial saved handler results for package \"" \
          [formatPackageName $package $version] "\" are " \
          [formatResult $code(1) $result(1)]]
    }

    #
    # NOTE: If the saved [package unknown] handler succeeded -AND- the
    #       package can now be loaded (or is somehow already loaded?),
    # NOTE: Did the saved [package unknown] handler succeed?
    #
    if {$code(1) == 0} then {
      #
      # NOTE: Is the package now available -OR- somehow already present?
    #       then skip running the repository handler.
    #
    if {$code(1) == 0 && ([isPackagePresent $package $version] || \
        [isPackageAvailable $package $version])} then {
      return
      #
      if {[isPackagePresent $package $version] || \
          [isPackageAvailable $package $version]} then {
        #
        # NOTE: Skip using the package repository.
        #
        return
      }
    }

    #
    # NOTE: Next, run our special [package unknown] handler.
    #
    if {[canDownloadPackage $package]} then {
      set code(2) [catch {