Learning Perl, 5th Edition

In this chapter, you will see a feature that makes Perl one of the world's great programming languageshashes.^[*] Though hashes are a powerful and useful feature, you may have used other powerful languages for years without ever hearing of hashes. But you'll use hashes in nearly every Perl program you'll write from now on; they're that important.

^[*] In the olden days, we called these "associative arrays." In about 1995, the Perl community decided this was too many letters to type and too many syllables to say, so we changed the name to "hashes."