There is no mention of a die_bug in the Perl core either in version v5.18.4 or v5.26.2, nor anywhere on PerlMonks. The most common mention I can find on the net, and the only mention on CPAN, is apparently in the source of GNU Parallel, where it is currently defined as follows:

sub die_bug {
    my $bugid = shift;
    print STDERR
    ("$Global::progname: This should not happen. You have found a bug.
+\n",
     "Please contact <parallel\@gnu.org> and follow\n",
     "https://www.gnu.org/software/parallel/man.html#REPORTING-BUGS\n"
+,
     "\n",
     "Include this in the report:\n",
     "* The version number: $Global::version\n",
     "* The bugid: $bugid\n",
     "* The command line being run\n",
     "* The files being read (put the files on a webserver if they are
+ big)\n",
     "\n",
     "If you get the error on smaller/fewer files, please include thos
+e instead.\n");
    ::wait_and_exit(255);
}
[download]

I don't know why you'd see a difference between Perl versions (Update: ... except for the difference between Linux and Windows, as noted by bliako. The following advice still applies). Please show a Short, Self-Contained, Correct Example that reproduces the issue, i.e. a short piece of code that works on v5.18 and fails on v5.26.