Using eval would delay the directive to runtime, but it needs to be active at runtime to affect code. 

>perl -e"eval 'use warnings; 1' or die $@; print undef;"

>perl -e"use warnings; print undef;"
Use of uninitialized value in print at -e line 1.

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And you can't wrap it in a BEGIN because that would introduce a lexical scope.

In reply to Re^2: use of "use X" by ikegami
in thread use of "use X" by bbfan

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