In fact, here's the implementation. This works in perl5 going back to uh... early? Have your cake today. Not that I tested it. It's simple enough I just penned this and didn't bother running it.
use Regexp::SlashN;
"A
B
C" =~ /(\N+)/;
$1 eq "A
B
C" or die;
Regexp/SlashN.pm
package Regexp::SlashN;
use overload;
sub import { overload::constant qr => \ &convert }
# A simple table of definitions
my %syntax = ( '\\' => '\\',
N => '[^\n]', );
sub convert {
my ( $re ) = @_;
$re =~ s/\\([\\N])/$syntax{$1}/g;
return $re;
}