I soon noticed that it was using local $/=undef. Which I gathered is generally frowned upon.

Eh? That's news to me.

Anyway, I see you're trying to read 64 bytes at a time, so you might think of setting $/ to a ref to a scalar containing the value 64. This will work:

local $/ = \64;
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as will

my $length = 64;
local $/ = \$length;
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After that, you can just read from the file with <HANDLE>, but I recommend calling binmode on the handle first, unless, maybe, you're absolutely sure you will only ever run this on Unix-like systems.

But I'd still do it anyway.