As others have pointed out, you should keep track up front but if that isn't possible a brute force approach would be to use find and the inode number:

#!/usr/bin/perl -w

use File::Find;

open( FH, "/etc/motd" ) || die "cannot open file ($!)\n";
$INO = (lstat(FH))[1];
close( FH );

find( \&wanted, '/etc' );

sub wanted {
   my( $ino ) = (lstat($_))[1];
   if( $ino == $INO ) {
      print $File::Find::name, "\n";
   }
}
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Caveats to this approach apply all over the place but it could be usefull if you have some inkling of where in the filesytem to start looking

-derby