In the free document for beginners, http://www.perl.org/books/beginning-perl/.. There is a mistake in chess game program at declaration part (not related to perl but Chess).
i.e in Chapter 7. References ( Page : 233 )
Now it is,
my @back = qw(R N B Q K N B R);
But it has to be,
my @back = qw(R N B Q K B N R);
That is : Chess pieces must be placed like mirror image for pieces R, N and B..
Left side : R N B
Right side: B N R