diff --git a/src/NodaWikidataFetcher.php b/src/NodaWikidataFetcher.php
index 98d9bc7..11e6aa6 100644
--- a/src/NodaWikidataFetcher.php
+++ b/src/NodaWikidataFetcher.php
@@ -83,9 +83,38 @@ final class NodaWikidataFetcher {
         '<p><span class="geo noexcerpt"',
     ];
 
+    const RETRIEVAL_MODES_ACCEPTED = [
+        'list',
+        'add',
+        'keep',
+        'replace',
+    ];
+
+    const RETRIEVAL_MODES_DEFAULT = 'list';
+
+    /** @var 'list'|'add'|'keep'|'replace' */
+    private string $_retrievalMode = self::RETRIEVAL_MODES_DEFAULT;
+
     /** @var MDMysqli */
     private MDMysqli $_mysqli_noda;
 
+    /**
+     * Sets the retrieval mode.
+     *
+     * @param string $retrievalMode New retrieval mode to set.
+     *
+     * @return void
+     */
+    public function setRetrievalMode(string $retrievalMode):void {
+
+        if (!in_array($retrievalMode, self::RETRIEVAL_MODES_ACCEPTED, true)) {
+            throw new Exception("Retrieval mode not in list of accepted retrieval modes: " . implode(',', self::RETRIEVAL_MODES_ACCEPTED));
+        }
+
+        $this->_retrievalMode = $retrievalMode;
+
+    }
+
     /**
      * Validates a Wikidata ID. A Wikidata ID must start with a capital Q and be
      * numeric otherwise.
@@ -549,25 +578,24 @@ final class NodaWikidataFetcher {
         $cinfo = $cergebnis->fetch_assoc();
         if (!empty($cinfo['persinst_kurzinfo']) and substr($cinfo['persinst_kurzinfo'], 0, 3) !== 'GND') {
 
-            if (isset($_GET['keep'])) {
-                if (!$_GET['keep'] || $_GET['keep'] === 'replace') {
+            switch ($this->_retrievalMode) {
+            case "add":
 
-                    $updatePersinstStmt->bind_param("si", $datafromwiki, $persinst_id);
-                    $updatePersinstStmt->execute();
-
-                }
-                else if ($_GET['keep'] === 'add') {
-
-                    $newDesc = $cinfo['persinst_kurzinfo'] . PHP_EOL . PHP_EOL . $datafromwiki;
-
-                    $updatePersinstStmt->bind_param("si", $newDesc, $persinst_id);
-                    $updatePersinstStmt->execute();
-
-                }
+                $newDesc = $cinfo['persinst_kurzinfo'] . PHP_EOL . PHP_EOL . $datafromwiki;
 
+                $updatePersinstStmt->bind_param("si", $newDesc, $persinst_id);
+                $updatePersinstStmt->execute();
                 $output = true;
-            }
-            else {
+                break;
+
+            case "replace":
+
+                $updatePersinstStmt->bind_param("si", $datafromwiki, $persinst_id);
+                $updatePersinstStmt->execute();
+                $output = true;
+                break;
+
+            default:
 
                 $tlLoader = new MDTlLoader("wiki_getter_persinst", $preflang);
                 echo self::generateHTMLHeadForWikidataFetcher($lang);
@@ -585,7 +613,7 @@ final class NodaWikidataFetcher {
                 echo '<br><a href="get_wikidata_for_persinst.php?wikidata_id=' . $wikidata_id . write_get_vars(['suchbegriff', 'lang', 'persinst_id']) . '&keep=replace" class="buttonLike icons iconsPinOff">Replace with new entry</a>';
                 echo '<br><a href="get_wikidata_for_persinst.php?wikidata_id=' . $wikidata_id . write_get_vars(['suchbegriff', 'lang', 'persinst_id']) . '&keep=add" class="buttonLike icons iconsPlusOne">Keep old and add new entry</a><br><br><br>';
 
-                 exit;
+                exit;
 
             }
 
@@ -939,20 +967,14 @@ final class NodaWikidataFetcher {
 
         if (!empty(trim($curPlaceInfo['ort_anmerkung'])) and substr($curPlaceInfo['ort_anmerkung'], 0, 3) !== 'GND') {
 
-            if (isset($_GET['keep'])) {
-
-                if ($_GET['keep'] === 'add') {
-
-                    $datafromwiki = $curPlaceInfo['ort_anmerkung'] . PHP_EOL . PHP_EOL . $datafromwiki;
-
-                }
-                else if ($_GET['keep'] === 'keep') {
-                    $datafromwiki = $curPlaceInfo['ort_anmerkung'];
-                }
-
-            }
-            else {
-
+            switch ($this->_retrievalMode) {
+            case "add":
+                $datafromwiki = $curPlaceInfo['ort_anmerkung'] . PHP_EOL . PHP_EOL . $datafromwiki;
+                break;
+            case "keep":
+                $datafromwiki = $curPlaceInfo['ort_anmerkung'];
+                break;
+            default:
                 $tlLoader = new MDTlLoader("wiki_getter_place", $preflang);
                 echo self::generateHTMLHeadForWikidataFetcher($lang);
                 echo self::generateWikidataFetcherHeader($tlLoader);
@@ -1349,25 +1371,24 @@ final class NodaWikidataFetcher {
 
         if (!empty($cinfo['tag_anmerkung']) and substr($cinfo['tag_anmerkung'], 0, 3) !== 'GND') {
 
-            if (isset($_GET['keep'])) {
-                if (!$_GET['keep'] || $_GET['keep'] === 'replace') {
+            switch ($this->_retrievalMode) {
+            case "add":
 
-                    $updateTagDescStmt->bind_param("si", $datafromwiki, $tag_id);
-                    $updateTagDescStmt->execute();
-
-                }
-                else if ($_GET['keep'] === 'add') {
-
-                    $newDesc = $cinfo['tag_anmerkung'] . PHP_EOL . PHP_EOL . $datafromwiki;
-
-                    $updateTagDescStmt->bind_param("si", $newDesc, $tag_id);
-                    $updateTagDescStmt->execute();
-
-                }
+                $newDesc = $cinfo['tag_anmerkung'] . PHP_EOL . PHP_EOL . $datafromwiki;
 
+                $updateTagDescStmt->bind_param("si", $newDesc, $tag_id);
+                $updateTagDescStmt->execute();
                 $output = true;
-            }
-            else {
+                break;
+
+            case "replace":
+
+                $updateTagDescStmt->bind_param("si", $datafromwiki, $tag_id);
+                $updateTagDescStmt->execute();
+                $output = true;
+                break;
+
+            default:
 
                 $tlLoader = new MDTlLoader("wiki_getter_tag", $preflang);
                 echo self::generateHTMLHeadForWikidataFetcher($lang);