I have not found an explanation as to why Perl was created like this. Surely there must be a reason for it...

I think this is due to the relationship between use being like a require in a BEGIN, which in turn is like a do FILE, which in turn is like an eval. eval returns undef when its code fails, and do also has slightly more complex error cases:

    unless ($return = do $file) {
        warn "couldn't parse $file: $@" if $@;
        warn "couldn't do $file: $!"    unless defined $return;
        warn "couldn't run $file"       unless $return;
    }
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As a side note: Acme::ReturnValue