Some of the character classes are not builtin to the perl binary but stored in external files (that are created when perl is installed). Maybe there's a problem loading these files??? Running the test under strace might help debug the problem. 
strace perl -e'" " =~ /\p{Unassigned}/'

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In reply to Re: unassigned utf8 by ikegami
in thread unassigned utf8 by Johnny Five Toes

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