my $config = $parser->parse(*CONFIG);

##</code><code>##

my $config = $parser->parse('main::CONFIG');

##</code><code>##

my $config = $parser->parse('*main::CONFIG');

##</code><code>##

sub something_that_stringifies { "$_[0]" }
my $fh = something_that_stringifies *CONFIG;
my $config = $parser->parse($fh);