A hash, or more technically an associative array, assigns a key to a value.
%food = ('fruit',banana,'vegetable',onion,'grain',bread);
The hash could also be written like this, which may be easier for some people to read.
%food(); $food(fruit) = banana; $food(vegetable) = onion; $food(grain) = bread;
You can then print the value of a hash item. For example, the following will print "banana".