$ cat /tmp/blam | sed 's/^/one: /'  &
$ cat /tmp/blam | sed 's/^/two: /' &
cat > /tmp/blam
one
two: one
two
one: two
three
two: three
four
one: four
five
two: five
six
one: six
seven
two: seven
eight
one: eight
nine
two: nine
ten
one: ten
^C
[2]  + done       cat /tmp/blam | sed 's/^/one: /'
[1]  + done       cat /tmp/blam | sed 's/^/two: /'