#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11123425
use warnings;

open FILNAM, '<', \<<END or die $!;
1234567890
abcdefghijkl
END

my $val = unpack 'H32', do { local $/ = \16; <FILNAM> };

print "$val\n";
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UPDATED: changed input to an in memory file to make program completely self contained.