if {[info exists $varName]} then {
      return [set $varName]
    }

    return ""; # NOTE: System default, which is "public".
  }

  proc getLookupVersion { requirement } {
    if {[set index [string first - $requirement]] != -1} then {
      incr index -1; set requirement [string range $requirement 0 $index]
    }

    if {[set index [string first a $requirement]] != -1 || \
        [set index [string first b $requirement]] != -1} then {
      incr index -1; set requirement [string range $requirement 0 $index]
    }

    if {$requirement eq "0"} then {
      set requirement ""
    } elseif {[regexp -- {^\d+$} $requirement]} then {
      append requirement .0
    }

    return $requirement
  }

  proc getLookupBaseUri {} {
    set varName [appendArgs [getLookupVarNamePrefix] base_uri]

    if {[info exists $varName]} then {
      return [set $varName]
    }

      error "package unknown handler is not hooked"
    }

    package unknown [set $varName]
    unset $varName
  }

  proc runSavedPackageUnknownHandler { package version } {
    #
    # NOTE: See if there is a saved [package unknown] handler.  If so, then
    #       attempt to use it.
    #
    set varName [appendArgs [getLookupVarNamePrefix] saved_package_unknown]
    set oldHandler [expr {[info exists $varName] ? [set $varName] : ""}]

    if {[string length $oldHandler] > 0} then {
      lappend oldHandler $package $version; uplevel #0 $oldHandler
    }
  }

  #
  # NOTE: This version argument to this procedure must be optional, because
  #       Eagle does not add a version argument when one is not supplied to
  #       the [package require] sub-command itself.
  #
  proc packageUnknownHandler { package {version ""} } {
    #
    # NOTE: First, run our [package unknown] handler.
    #
    if {[catch {main $package $version} error(1)] == 0} then {
      #
      # NOTE: The repository [package unknown] handler succeeded, run the
      #       saved [package unknown] handler.
      #
      if {[catch {
        runSavedPackageUnknownHandler $package $version
      } error(2)] == 0} then {
        #
        # NOTE: Success?  Just return and let Tcl (or Eagle) handle the
        #       rest.  This is the "happy" path.
        #
        return
      } else {
        #
        # NOTE: Failure?  Attempt to log the error message.
        #
        catch {
          tclLog [appendArgs \
              "pkgr: saved handler failed for \"" [appendArgs [string \
              trim $package " " $version]] "\", error: " $error(2)]
        }
      }
    } else {
      #
      # NOTE: Failure?  Attempt to log the error message and then maybe
      #       try the original [package unknown] handler.
      #
      catch {
        tclLog [appendArgs \
            "pkgr: new handler failed for \"" [appendArgs [string \
            trim $package " " $version]] "\", error: " $error(1)]
      }

      #

      # NOTE: The repository [package unknown] handler failed, run the
      #       saved [package unknown] handler anyway.  There is almost


      #       no chance of this actually providing the package.





      #
      if {[catch {
        runSavedPackageUnknownHandler $package $version

      } error(2)] == 0} then {
        #
        # NOTE: Success?  Just return and let Tcl (or Eagle) handle the
        #       rest.
        #
        return
      } else {
        #

    error [array get error]
  }

  proc main { package version } {
    #
    # NOTE: Issue the lookup request to the remote package repository.
    #
    set data [getLookupData \
        [getLookupApiKey] $package [getLookupVersion $version]]

    #
    # NOTE: Attempt to grab the lookup code from the response data.
    #
    set code [getLookupCodeFromData $data]

    #