chipmunk accurately identified the source of my problem. I had thought I was copying the filehandles, but I was actually dup'ing globs, so I was stomping the filehandle value anyway. Unfortunately, the fileno approach is only useful if I use it everywhere in my code, which I didn't, for other reasons. I did, however, manage to put together a solution that works exactly as desired, massaging things into the approach suggested in perlfunc:open:

# Save the previous filehandles for STDOUT and STDERR so we
# can restore them when we're done.
local *REAL_STDOUT;
local *REAL_STDERR;
open(REAL_STDOUT, ">&STDOUT");
open(REAL_STDERR, ">&STDERR");
$this->{'_stdout'} = *REAL_STDOUT;
$this->{'_stderr'} = *REAL_STDERR;

# Set the new filehandles for STDOUT and STDERR
local *STDOUT_LOG;
local *STDERR_LOG;
*STDOUT_LOG = $this->{'stdout_log'};
*STDERR_LOG = $this->{'stderr_log'};
open(STDOUT, ">&STDOUT_LOG");
open(STDERR, ">&STDERR_LOG");
[download]

I can restore STDOUT and STDERR later with this code:

if(defined($this->{'_stdout'}))
{
    local *REAL_STDOUT;
    *REAL_STDOUT = $this->{'_stdout'};
    open(STDOUT, ">&REAL_STDOUT") or warn "Couldn't restore STDOUT: $!
+";
    print STDOUT "STDOUT restored\n";
    undef($this->{'_stdout'});
}
if(defined($this->{'_stderr'}))
{
    local *REAL_STDERR;
    *REAL_STDERR = $this->{'_stderr'};
    open(STDERR, ">&REAL_STDERR") or warn "Couldn't restore STDERR: $!
+";
    print STDOUT "(STDERR restored)\n";
    print STDERR "STDERR restored\n";
    undef($this->{'_stderr'});
}
[download]

Everything's happy now.

--isotope
http://www.skylab.org/~isotope/