Perl Problem

If this technique is not used, it would mean rewriting the whole compiler for each target machine. With this technique, all the 'clever stuff' is done in in going from the high level to the intermediate code, leaving a relatively simple task for producing output for different targets.

It also means changes to the rules in the high level compiler don't change anything in the second stage of compilation (you could even change to a different language, as long as it produced the same intermediate code).