In particular, from open:

Here is a script that saves, redirects, and restores STDOUT and STDERR using various methods:

    #!/usr/bin/perl
    open(my $oldout, ">&STDOUT") or die "Can't dup STDOUT: $!";
    open(OLDERR, ">&", \*STDERR) or die "Can't dup STDERR: $!";
    open(STDOUT, '>', "foo.out") or die "Can't redirect STDOUT: $!";
    open(STDERR, ">&STDOUT") or die "Can't dup STDOUT: $!";
    select STDERR; $| = 1; # make unbuffered
    select STDOUT; $| = 1; # make unbuffered
    print STDOUT "stdout 1\n"; # this works for
    print STDERR "stderr 1\n"; # subprocesses too
    open(STDOUT, ">&", $oldout) or die "Can't dup \$oldout: $!";
    open(STDERR, ">&OLDERR") or die "Can't dup OLDERR: $!";
    print STDOUT "stdout 2\n";
    print STDERR "stderr 2\n";
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