Has something changed in the Free Pascal environment that would prevent some units from being found?
On 2010-10-14 I submitted a Free Pascal solution that used the "contnrs" unit - this got WA. I can see from an earlier compilation error that Free Pascal v2.2.4-3 was in use at the time.
I've just tried re-submitting exactly the same code, and this now gets a compilation error that the "contnrs" unit cannot be found. This is with Free Pascal v2.6.4+dfsg-4.
Please can we have the contnrs unit back?