perl - Why use strict and warnings?

Question

It seems to me that many of the questions in the Perl tag could be solved if people would use:

use strict;
use warnings;

I think some people consider these to be akin to training wheels, or unnecessary complications, which is clearly not true, since even very skilled Perl programmers use them.

It seems as though most people who are proficient in Perl always use these two pragmas, whereas those who would benefit most from using them seldom do. So, I thought it would be a good idea to have a question to link to when encouraging people to use strict and warnings.

So, why should a Perl developer use strict and warnings?

Answer 1

For starters, use strict; (and to a lesser extent, use warnings;) helps find typos in variable names. Even experienced programmers make such errors. A common case is forgetting to rename an instance of a variable when cleaning up or refactoring code.

Using use strict; use warnings; catches many errors sooner than they would be caught otherwise, which makes it easier to find the root causes of the errors. The root cause might be the need for an error or validation check, and that can happen regardless or programmer skill.

What's good about Perl warnings is that they are rarely spurious, so there's next to no cost to using them.

---

Related reading: Why use my?