It started with Go's defer functionality. Someone came up with a GCC solution. Another person found a way with clang. This makes them syntactically the same.

defer {
	if (close (fd) < 0) {
		printf ("Failed to close close.c: %s\n", strerror (errno));
	}
};

While generally a thing of the past, atomic deployments were a fun challenge. Using this module you could have multiple DocumentRoot paths, one of which was selected by a symlink. Because your code saw the DocumentRoot as the actual path and not the symlink, you could change the symlink and in-flight requests would not be affected. This prevents mixing of code versions and the issues associated.

<VirtualHost *:80>
	DocumentRoot /var/www/example.com/htdocs
	SymlinkAt /var/www/example.com
</VirtualHost>

It's niche problem, but for organizations hosting lots of sites it can be important to know when a site's hostname should have www in front of it. The daemon bases this decision on the number of DNS labels that exist when the TLD is removed from the hostname. Uses data from Mozilla's Public Suffix List initiative.

RewriteLock /tmp/rewrite.lock
RewriteMap wwwify prg:/usr/local/bin/wwwify -t /etc/tlds.dat -T -s /tmp/wwwify.stats

RewriteCond ${wwwify:%{HTTP_HOST}|%{HTTP_HOST}} ^(www\.[a-z0-9_.-]+)$ [NC]
RewriteCond %1 ^((?!%{HTTP_HOST}))$ [NC]
RewriteRule ^(.*) %{ENV:X_REQ_PROTOCOL}://%1$1 [R=permanent,L]

Originally a Bash script that used Netflix's Denominator to sync changes, this was a complete recreation. Fully self-contained with no external dependencies beyond Perl, it enabled syncing to, from, and between local zone files, AWS Route53, Dynect, and NS1.