use IPC::Open2;
use POSIX ":sys_wait_h";

my $pid = open2 ( REA, WRI, 'tr a-z A-Z' ) or die $!;
for  (<DATA>){
    print {\*WRI}  [(my $cmd, my @rest) = split]->[0];
}
close WRI;
print <REA>;
close REA; # but believe it or not, under sysV the zombie is still there!
waitpid($pid,0); # this will finally kill it cleanly!
__END__ # although exit from the program will eventually kill it of course
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