my $path = '\nbs\main\den\rel_10.\cr_Q00472526-03-1\final';
   $path =~ s/[^\\]+\\(\w+)$/$1/ ;
   print $path;

__END__
\nbs\main\den\rel_10.\final

##</code><code>##


   my ($leaf ) = $path =~ m/[^\\]+$/g ;  #save the leaf
   $path =~ s/(.+)\\.+\\$leaf$/$1/;      #prune the branch
   $path .= "\\$leaf";                   #graft the leaf
   print "$path\n";

__END__
\nbs\main\den\rel_10.\final