Mine

# Usage: domains_list.sh <input> <thruput> <output> <combos> <suffix> <delay> <retries>

input=$1; thruput=$2; output=$3; combos=$4; suffix=$5; delay=$6; retries=$7

# Mix the names together
#
function mix () {

    if (($1 < 1)); then echo "$2.$suffix"
		
        else for x in "$input"; do echo "$(mix $(($1-1)) $x$2)"; done
	
    fi 
    
}

names=$(mix $combos)

# If they're available, let us know
#
for name in $names; do

    tries=0

    while ((tries<retries)); do

        result=$(whois "$name" 2>&1) || { ((tries++)); sleep 1; continue; }

        if grep -q 'No match' <<< "$result"; then
        
			echo "+ $name"; echo $name >> "$output"
			
			else echo "- $name"
			
		fi

        break

    done

    # Server error?
    #
    if ((tries==3)); then echo "/ $name"; fi

    # Sleep for a while
    #
    sleep $delay

done