'use' is parsed at compile time. Unless the 'use' statement and the assignment to $req_File are inside a BEGIN block, I would expect it to fail since no value has been assigned to $req_File. I'm not sure 'use' accepts a scalar as an argument. If you need the functionality of 'use' at runtime, use eval "use $req_File".

---
print map { my ($m)=1<<hex($_)&11?' ':'';
$m.=substr('AHJPacehklnorstu',hex($_),1) }
split //,'2fde0abe76c36c914586c';
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