I'm by no means sure about whay you're really asking -but that may just be me-. Why don't you put the unless ($return = do $file) { # etc code inside the block of the second if clause?

Or else, why don't you use some alternate flow control construct? For example:

for ($file) {  # for aliasing too
    last unless -e;
    unless (my ret=do $_) {
    # ...
    }
}
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or something like that;

But seriously, you may consider making that file into a proper module...