expr has :

install.sh

@@ -80,7 +80,7 @@ while read line
 do
   if expr "${line}" : "^[[:alnum:]_]\+=" 1>/dev/null
   then
-    var_name="$(expr "${line}" "^\([[:alnum:]_]\+\)=")"
+    var_name="$(expr "${line}" : "^\([[:alnum:]_]\+\)=")"
 
     if [ -n "$(grep "^${var_name}=" /home/joeac.net/joeac.net/.env)" ]
     then
@@ -89,7 +89,7 @@ do
 
     if [ -z "${!var_name}" ]
     then
-      default_value="$(expr "${line}" "^[[:alnum:]_]\+=\(.*\)\$")"
+      default_value="$(expr "${line}" : "^[[:alnum:]_]\+=\(.*\)\$")"
       read -sp "${var_name}: " ${var_name}
       if [ -z "${!var_name}" ]
       then