I somehow suspect that this is more due to the platform difference than different perl versions. In particular you could check if the line endings differ on both platforms, and if they were removed correctly.

A good way to print strings that might contain non-printable characters is Data::Dumper:

use Data::Dumper;
local $Data::Dumper::Useqq = 1;
...
print Dumper($str_eval);
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