the hazards of coding for webservers vs. shell scripts

[kareila]

When I was doing some code cleanup a few months ago, I saw some lines that looked like this:

my $foo;
$foo = $bar unless $baz;

I decided that looked redundant and changed it to:

my $foo = $bar unless $baz;

Take my advice: don't combine "my" statements and postfix conditionals. Ever.

I've updated the programming guidelines to warn people away from this as well.

The manifestation of this particular bug was to cause the $foo variable to be referenced in global scope if the conditional was false. In that situation, the assigned value would persist across execution threads, such that if two people in a row had a true $baz, the second user would see the first user's value of $foo. Even with use warnings and use strict in effect, Perl apparently thinks this is perfectly fine.

ETA: exor674 says this command will find it (but not in BML files):

perlcritic --single-policy ProhibitConditionalDeclarations

Comments

[sophie]

I must admit, I'm mostly the same; I also don't tend to use unless at all, as my brain prefers consistency; I can deal with negated ifs.

But of course I stick to the coding guidelines for DW.