proc getLookupApiKey {} {
    set varName [appendArgs [getLookupVarNamePrefix] api_key]

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



    global env

    set varName [string trim $varName :]


    if {[info exists env($varName)]} then {




      return $env($varName)




    }

    return ""; # NOTE: System default, which is "public".
  }

  proc getLookupBaseUri {} {
    set varName [appendArgs [getLookupVarNamePrefix] base_uri]

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

    global env
    set varName [string trim $varName :]

    if {[info exists env($varName)]} then {
      return $env($varName)
    }

    return https://urn.to/r/pkg; # NOTE: System default.
  }

  proc getLookupUri { apiKey package version } {
    set baseUri [getLookupBaseUri]

      package require http 2.0

      return [appendArgs \
          $baseUri ? [http::formatQuery raw 1 method lookup apiKey $apiKey \
          package $package version $version]]
    }
  }

  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 getLookupData { apiKey package version } {
    set uri [getLookupUri $apiKey $package $version]

    if {[string length $uri] == 0} then {
      return ""
    }