I don't think this would not be a significant cost. Only the package declaration would have to be checked (and there is already some checking of package names); everything else would work out to a normal syntax error or a nonexistent package error.
That said, I'm fine with Perl's "if you want to do something stupid, who are we to stop you?" philosophy.
In reply to Re^2: Perl allows package names consisting entirely of colons
by ColonelPanic
in thread Perl allows package names consisting entirely of colons
by tobyink
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