open SHELL, "| bash.exe" or die "can't open the shell: $!";

print SHELL "type C:/temp.ml | ocaml > C:/output.txt\n";

print SHELL "dir C:/output.txt\n";

# and so on...

##</code><code>##

open TEMP, "C:/temp.ml" or die "C:/temp.ml: $!";
open CAML, "| ocaml > C:/output.txt" or die "can't run ocaml: $!";

while (<TEMP>) { print CAML }
close CAML;

open TXT, "C:/output.txt" or die "C:/output.txt: $!";
while (<TXT>) {
    # do other stuff
}