Strange indeed. I can only produce the problem when running the debugger in that specific directory on that platform. When I copy the program to the next higher directory and run the program in that directory, I get normal results:

$ cd -
/home/jkeenan/learn/perl
$ cat abc.pl
print "hello world\n";
print "goodbye world\n";
$ perl -d abc.pl

Loading DB routines from perl5db.pl version 1.49_04
Editor support available.

Enter h or 'h h' for help, or 'man perldebug' for more help.

main::(abc.pl:1):    print "hello world\n";
  DB<1> c
hello world
goodbye world
Debugged program terminated.  Use q to quit or R to restart,
use o inhibit_exit to avoid stopping after program termination,
h q, h R or h o to get additional info.
  DB<1> q
[download]

And when I run the program through the debugger in a directory with the same name on a different platform (a FreeBSD-11.0 VM on the same box), I get expected results.