Perl's map() function runs an expression on each element of an array, and returns a new array with the results.
@LIST = map(EXPRESSION, @ARRAY);
Think of the @myNames array as a row of numbered boxes, going from left to right, numbered starting with a zero. The map() function goes through each of the elements (boxes) in the array, and runs the EXPRESSION on their contents. The altered contents are then added to the new @ucNames array.
@myNames = ('jacob', 'alexander', 'ethan', 'andrew'); @ucNames = map(ucfirst, @myNames);
In the above example, EXPRESSION is the built-in function ucfirst that makes the first letter of the word upper case. After running the expression on each element of the @myNames array, the value of @ucNames becomes ('Jacob', 'Alexander', 'Ethan', 'Andrew').