Perl Debugged

Chapter 5. Tracing Code

“1545 Relay #70 Panel F (moth) in relay. First actual case of bug being found.”

—Admiral Grace Hopper's Logbook September 9, 1945

In the phylogeny of debugging, the Protozoic approach consists of tossing

print "\$variable = $variable\n";

lines into the problem code at various places. Before we advance up the evolutionary ladder to interactive debuggers in Chapter 7, however, we have a lot of ground to cover.

We should not so readily disparage the humble print statement, because with a little tuning it can turn into a valuable tool. As we've already seen, the most basic kind of tracing statement prints out a variable ...