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> If no error is ever thrown, then nobody knows and nobody cares and there is nothing to fix.

Wrong, as you can see from the code I posted, not only the sub is affected, but the intended side-effect (of altering the call-by-reference argument) is missing without warning.

in continuation of Re^3: ref to read-only alias ... why? (not consistent)

  DB<111> $x=0; for ($x,0) { print; inc_b($_); print " -> $_\n"}
0 -> 1
0 -> 0
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> So, yes, exactly as I said, the worst possible case can be solved by adding a simple eval around the code that modifies the reference

How is eval supposed to help here?

> but is (badly) designed to also tolerate the failure in the case of read-only parameters.

So in your opinion manipulating $_[0] is a bad design!?!

Could you please post some code-examples to illustrate your point of view?