oops - thought I got that one.

vars/retrieveEnvVars.groovy

@@ -2,8 +2,10 @@ def call(String containerName, List<String> envVars) {
     container(containerName) {
         script {
             envVars.each {  var ->
+                echo "Exporting ${containerName} variable ${var} to Jenkins..."
                 env."$var" = sh(script: "echo \$$var", returnStdout: true).trim()
             }
         }
+        echo "Finished exporting variables for container ${containerName}"
     }
 }