Expect includes a fork. So does TclX.
Example:
for {set i 0} {$i < 100} {incr i} {
set pid [fork]
switch $pid {
-1 {
puts "Fork attempt #$i failed."
}
0 {
puts "I am child process #$i."
exit
}
default {
puts "The parent just spawned child process #$i."
}
}
}