A form of brain-damage in those who program too much in the write-only computer language Perl.
In it's most basic form, a Perl programmer will use Perl to accomplish common tasks for which other more appropriate (and easier) tools already exist. In extreme cases, those suffering from Perl Syndrome will set their login shell to Perl, and replace system executables with their own Perl monstrosities.
When confronted with evidence that they have Perl syndrome, one afflicted will become upset, deny that there's anything wrong, and respond "TMTOWTDI" ("There's More Than One Way To Do It" - Perl's motto.)
Asked by a newbie how to log the output of syslog to another host (a common Unix task), someone with Perl Syndrome replied that the 'easiest' way would be to write a 'simple' 25-line Perl script that would open a TCP connection to the remote host, tail the appropriate logfile, and write them out (another 'simple' Perl script would of course need to be written to accept and process this TCP connection.)
To the sufferer of Perl Syndrome, this was all simpler and easier than just enabling 'remote host' in the syslog configuration.