#One piece of data can be used as a reference to some other piece of data.
#Sometimes the piece of data is called a pointer (Pascal or C).

#normal scalar example
print ":: Normal scalar example ::\n";
$a="Stones";  
$b=$a;
print '$a = ',"$a\n";
print '$b = ',"$b\n";
$a = "Bread";
print 'after changing only $a';
print "\n";
print '$a = ',"$a\n";
print '$b = ',"$b\n";
print "\n";

#reference example, $ref -> $a, $ref contains address
print ":: Reference example 1 ::\n";
$a="Stones";  
$ref=\$a;		#syntax to create pointer to some scalar
print '$a = ',"$a\n";
print '$ref = ',"$ref #this is a meaningless memory address\n";
print '$$ref = ',"$$ref\n";  #syntax two $$ to follow reference
$a = "Bread";
print 'after changing only $a to bread';
print "\n";
print '$a = ',"$a\n";
print '$$ref = ',"$$ref\n";
print "\n";

#reference example, $ref -> $a, $ref contains address
print ":: Reference example 2 ::\n";
$a="Stones";  
$ref=\$a;	
print '$a = ',"$a\n";
print '$$ref = ',"$$ref\n";  
$$ref = "Sticks";
print 'after changing only $$ref to sticks';
print "\n";
print '$a = ',"$a\n";
print '$$ref = ',"$$ref\n";
print "\n";

print ":: Reference example 3, to break a reference ::\n";
$ref = "Break";  #assign it to a scalar
print '$ref = ',"$ref\n";
print "\n";

print ":: Reference example 4, chain references ::\n";
$book = "Lord of the Rings";
$bref = \$book;
$bref2 = \$bref;  
print '$$$bref2 = ',"$$$bref2\n";
print "\n";

print ":: Reference example 5, reference to Arrays ::\n";
@trees = qw (oak cedar maple apple);  #quick word keyword
$aref = \@trees;  #point to array
print $$aref[0],"\n";  
print @$aref[0],"\n";	#same effect
print "\n";

print ":: List of Lists, something like 2D array (not exactly the same) ::\n";
@list_of_lists = (
	[qw (Mustang Bronco Ranger)],
	[qw (Cavalier Suburban Buick)],
	[qw (LeBaron Ram)],
);
print "row 0, col 1 = ",$list_of_lists[0][1],"\n"; 
print "Last element (no of rows) = ",$#list_of_lists,"\n"; 
print "Last element (no of columns) of row 1 = ",$#{$list_of_lists[1]},"\n";
#there are other better ways to declaring, like using push