I wonder about this also. Annoying to kind of have to convert that in your head when reading older style instruction (Network Programming with Perl by Stein) that use barewords all over the place when the newer guidance is to use lexical filehandles. I think that the short answer is that the bareword is the old way to do it, and now you should use lexical variables because they limit the scope. This seems to confirm:

#!/usr/bin/env perl
use strict;
use warnings;

{
open (OUTPUT,"> out.txt") or die;
}

print OUTPUT "a"; # Works OUTPUT must still be in scope

{
open (my $new_out, ">","new_out.txt") or die $!;
print $new_out "b";
}

#print $new_out "c"; #this will not work
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