c:\@Work\Perl\monks\Veltro>perl -wMstrict -MData::Dump -le
"my %RE = (
   '\\\\/' => 'BackBackFwd1',
   '\\\/'  => 'BackBackFwd2',
   '\\/'   => 'BackFwd1',
   '\/'    => 'BackFwd2',
   '/'     => 'Fwd',
   );
 dd \%RE;
 ;;
 my $rx = qr{ $RE{'\\\\/'} $RE{'\\\/'} $RE{'\\/'} $RE{'\/'} $RE{'/'} };
 print $rx;
"
{ "/" => "Fwd", "\\/" => "BackFwd2", "\\\\/" => "BackBackFwd2" }

(?^: BackBackFwd2 BackBackFwd2 BackFwd2 BackFwd2 Fwd )