How can return fail? Perl's warning is spot-on. If you want to croak when the return value isn't true, that needs to be associated with the sub call, not the return call. Precedence takes care of that, and you can still use or if you add parens:

$ perl -Mstrict -wE'sub foo{} sub bar{return foo() or die "died"} bar(
+)'

Possible precedence issue with control flow operator at -e line 1.
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$ perl -Mstrict -wE'sub foo{} sub bar{return foo() || die "died"} bar(
+)'

died at -e line 1.
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$ perl -Mstrict -wE'sub foo{} sub bar{return (foo() or die "died")} ba
+r()'

died at -e line 1.
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Hope this helps (but you already got it I reckon...)!