Shell Programming and Scripting

I've been diving into awk but still learning how to use it for text formatting. Below you can see my results are separated by a comma. Can somebody show me how to separate by TAB as well? An explanation would be appreciated as I did not comprehend the answer in the man pages and would like to gain a better understanding. Thanks!

Input example .txt carriage return between URLs:

www.google.com
www.yahoo.com
www.aol.com

Code:

DEST=~/Desktop/ipout.txt

Echo 'Drag file here and press enter'
read SRC

echo '
Evaluating IP Range, please wait...'
awk '{print $1}' < $SRC |
while read ip;
do
echo $ip && curl -s --head $ip | head -n 1
done | awk 'ORS=NR%2?", ":RS' > $DEST
echo 'Complete. Results can be found at' $DEST

Output reads:

www.google.com, HTTP/1.1 200 OK
www.yahoo.com, HTTP/1.1 301 Redirect
www.aol.com, HTTP/1.1 200 OK

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Replace a "space" for a string in while loop

Thank You.

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