One way to avoid use strict and use warnings being inherited by your evaled source is to simply no strict; no warnings; before you eval.

To avoid lexical variables, put the eval() in a subroutine that appears before any file scoped lexicals (and before the pragmas too).

# Start of program

sub myeval { eval shift }

use strict;
use warnings;
# ...rest of program
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A completely different approach would be to put a code reference into @INC. That way you can actually use require.