#!/usr/bin/perl -wl
$| = 1; # unbuffered output
print $$;
for(1,2){
    open SAVEOUT,">&STDOUT";
    my $pid = open STDOUT,"| tee log_$_";
    open STDERR, ">&STDOUT";
    print "this goes to STDOUT (log_$_)";
    warn "This goes to STDERR (log_$_)";
    sleep 1;
    print "killing $pid";
    kill 15, $pid;
    close STDOUT;
    close STDERR;
    open STDOUT,">&SAVEOUT";
}
__END__
Name "main::SAVEOUT" used only once: possible typo at tee.pl line 4.
14781
this goes to STDOUT (log_1)
This goes to STDERR (log_1) at tee.pl line 8.
killing 14782
this goes to STDOUT (log_2)
This goes to STDERR (log_2) at tee.pl line 8.

##</code><code>##

$ cat log_1 log_2
this goes to STDOUT (log_1)
This goes to STDERR (log_1) at tee.pl line 8.
this goes to STDOUT (log_2)
This goes to STDERR (log_2) at tee.pl line 8.