I chose 300 for two reasons: it's a reasonable guess at what the OP might mean by 'some hundreds', and even the slowest configuration technique I tried meets the time criteria the OP gave for a configuration file of that size.

The slurp solution wasn't intended as a reliable way to handle configuration information, but as an indicative upper limit for a Perl solution to the problem. It's interesting to note however that fastconfig uses the same file format and has the same potential issues as the slurp solution.