That claim notwithstanding, try this:

#!/usr/bin/perl -w
use strict;

my $fh = 'OUT';
open ($fh, "< $0") or die "Cannot read $0: $!";
print <$fh>;
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Try replacing some of the $fh's with 'OUT'. Some combinations will work, some will fail. The list that works/fails changes from 5.005 to 5.6.

Caveat programmer.