#$ shifting themes, upon first glance        #
#      can the heart and soul really keep    #
#  up with the themes of our lives?         $#

our @themes = qw(
   fuel fire
    flame hot
     air water
    earth spirit
   desire love
    happiness peace
);

our $poem = q(
   from heart comes soul
    thus the heart is truly soul
     for without heart, one cannot have soul
    and without soul one returns to the heart
   one soul, one heart
    no heart, no soul
);

while(my $heart = shift @themes and my $soul = shift @themes)
   { $poem =~ s/heart/$heart/ && $poem =~ s/soul/$soul/ }
                       print $poem;

#$ is the theme shifting,                   #
#              or does it remain the same? $#