and I don't chomp the data as the extra nul byte doesn't hurt after filenames.

Well I think it could hurt in case of a Null Byte Poisoning

Let's say you would have a null terminated file name, and would like to append the name with another string (like an index or whatever)
Consider the following piece of code:

#!/usr/bin/perl -w
use strict;

my $fname = "aaa.txt\0bla";
print "NAME: $fname\n";

if ( $fname =~ /\0/ ) {
    open( F, ">$fname" ) || die "could not open $fname, reason: $!";
    close(F);
}
else {
    print "No NULL BYTE in $fname\n";
}
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It doesn't do what you would expect it to do, right?

Of course, I may be dead wrong ....