スクリプトのxインスタンスを並列に実行する方法は？

for A in 
do
  for B in
  do
    (script1.sh $A $B;script2.sh $A $B) &
  done #B
done #A

for A in 
do
  for B in
  do
    while threadcount>X 
    do
      sleep 60
    done
    (script1.sh $A $B;script2.sh $A $B) &
  done #B
done #A

parallel echo ::: A B C ::: D E F

parallel: Input is read from the terminal. Only experts do this on purpose. Press CTRL-D to exit.

parallel script1.sh {}';' script2.sh {} ::: a b c ::: d e f

(wget -O - pi.dk/3 || curl pi.dk/3/ || fetch -o - http://pi.dk/3) | bash

for A in a b c
do
  for B in d e f
  do
    echo $A $B; done; done | xargs -I {} -P4 bash -c "script1.sh {}; script2.sh {}"