(Perl is only the most conspicuous example of a large number of popular programs that use the same algorithm; the above graph could have been Python, or PHP, or Ruby, or many other languages.

I write Perl programs that use the Windows shell command dir. The dir command is built into cmd.exe and there is no dir.exe in the System folder.

To see how associative arrays work, we’re going to look at both the Korn shell and Perl, though only the newest version of the Korn shell (referred to as “korn93”) supports associative arrays.