only trigger if !ping is beginning of line

bot.ps1

@@ -185,7 +185,7 @@ function Join-Pong {
     )
 
     if($Ball) {
-        $padded_ball = $Ball+' '
+        $padded_ball = '"{0}" ' -f $Ball
     }
 
     $body = '{0}: Pong! (ping {1}took {2} to arrive)' -f $SenderMxId,$padded_ball,$ReadableTimespan
@@ -207,7 +207,7 @@ function Open-JoinEvent {
     )
 
     #the "ball" is a string returned by the bot
-    if($Event.content.msgtype -eq 'm.text' -and $Event.content.body -match '!ping( (?<ball>.*))?') {
+    if($Event.content.msgtype -eq 'm.text' -and $Event.content.body -match '^!ping( (?<ball>.*))?') {
         $difference = Compare-Timestamps -OriginServerTs $Event.origin_server_ts
         $readable_timespan = ConvertTo-HumanReadableTimespan -TimeSpan $difference