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".

print $food{fruit};