The thing I cant seem to figure is how to read the last line of 56 bytes.

How about getting the size, performing a little arithmetic and then seek-ing to the position of the last record?

my $recsize = 56;

open(FILE, $file) or die "open: $!";
my $size = -s FILE;
my $pos = int($size / $recsize)*$recsize;
seek(FILE, $pos, 0) or die "seek: $!";
read(FILE, my $out, $recsize) == $recsize or die "read: $!";
...
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