I managed to find out why my initial  eval " use ..." attempt failed. use; cannot be used in expressions . Hence, it does not return a value (so it's practically useless in truth evaluation constructs) even on a successful run like in the following.. 
eval "use Foo::Bar" or do { warn "eval failed" }

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Here eval"" always evaluates to false as use; returns nothing and we end up with the do BLOCK always being executed.

But getting eval"" to return a TRUE value on a successful eval changes that. 
eval "use Foo::Bar; 1" or do { warn "eval failed" }

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In reply to Re^2: BEGIN and compile-time by Firefly258
in thread BEGIN and compile-time by jbert

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