Your favorite trick can break some things. I just avoid copying or localizing globs that contain open file handles as I find there are too many egde cases where things break.

I much prefer to use the technique documented directly in the open documentation. Here is a modified version of it that doesn't bother with STDERR:

open( OLDOUT, ">&STDOUT" );
open( STDOUT, '> foo.out' )
    or  die "Can't redirect STDOUT to foo.out: $!\n";

# this works for subprocesses and C code too:
print "stdout 1\n";

close( STDOUT );
open( STDOUT, ">&OLDOUT" );
close( OLDOUT );
[download]

You can use a non-bareword file handle in place of OLDOUT, if you prefer.