Regex pattern objects are magical. Overloading doesn't even come into play.

Magical is right. This took me by surprise.

use overload;
use Scalar::Util qw( blessed );
use Test::More 'tests' => 4;

my $rx = qr/a/;

ok blessed $rx, 'Regexp is blessed';
ok ! overload::Overloaded( $rx ), 'Regexp is overloaded';
ok ! overload::Method( $rx, q{""} ), 'Regexp has q{""} overloaded';

isnt "$rx", overload::StrVal( $rx ),
     'StrVal of regexp isnt regexp stringified';
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