try using binmode
heres an example:

#!/usr/bin/perl
use Digest::MD5 ;
use warnings ;
use strict ;

foreach (@ARGV)
{
    open(FILE, "$_") or die "Can't open '$_': $!";
    binmode(FILE);
    print Digest::MD5->new->addfile(*FILE)->hexdigest, " $_\n";
}
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