The modules are core and your producing a maximal seed.

Still think it's exaggerated for your problem...

... but it's a good generic solution for similar tasks! =)

My only concern is readability, better use something like ord $char with an explicit loop var my $char

Anyway you are still operating on the assumption that hostnames are always different, since I don't know your project this might be ok or not.

Generating a random seed at installation time would prevent this "problem".