diff --git a/tools/append_or_replace b/tools/append_or_replace
index 7772383..ebf5320 100755
--- a/tools/append_or_replace
+++ b/tools/append_or_replace
@@ -13,10 +13,10 @@ REGEX=$1
 STRING=$2
 FILE=$3
 
-if ! grep -Pq "$REGEX" "$FILE"; then
+if ! grep -Eq "$REGEX" "$FILE"; then
 	printf "%s\n" "$STRING" >>$FILE
 	echo appended
 else
-	sed -i "s|$REGEX|$STRING|g" $FILE
+	sed -Ei "s|$REGEX|$STRING|g" $FILE
 	echo replaced
 fi