Update update_primary_nginx.yml -trying another approach

.github/workflows/update_primary_nginx.yml

@@ -25,8 +25,21 @@ jobs:
       #  run: envsubst  < ./nginx_template.txt > temp_default.conf
       # Maybe look at https://www.baeldung.com/linux/envsubst-command to get an idea
 
-      - name: Create temporary nginx config file
-        run: perl -pe 's/\$(\w+)/$ENV{$1}/ge' ./nginx_template.txt > temp_default.conf
+      - name: Replace Nginx variables with placeholders
+        run: |
+          sed 's/\$http_host/__HTTP_HOST__/g' ./nginx_template.txt | \
+          sed 's/\$remote_addr/__REMOTE_ADDR__/g' | \
+          sed 's/\$proxy_add_x_forwarded_for/__PROXY_ADD_X_FORWARDED_FOR__/g' > ./nginx_template_placeholder.txt
+
+      - name: Substitute environment variables
+        run: |
+          envsubst < ./nginx_template_placeholder.txt > temp_default.conf
+
+      - name: Restore Nginx variables
+        run: |
+          sed -i 's/__HTTP_HOST__/$http_host/g' temp_default.conf | \
+          sed -i 's/__REMOTE_ADDR__/$remote_addr/g' | \
+          sed -i 's/__PROXY_ADD_X_FORWARDED_FOR__/$proxy_add_x_forwarded_for/g'
 
       - name: Copy temporary file to correct place 
         run: cp -L temp_default.conf /etc/nginx/conf.d/default.conf