[delano@blackbox test]$ cat junk1
digraph "db-a12" {
        size="6,2.75";
        page="8.5,11";
	margin="1";
[delano@blackbox test]$ cat warnproblem.pl
open I , "junk1";
@b = <I>;
close I;
@c[0] = "\tmargin=\"1\";\n";
warn "entering xxx\n";
xxx( @c);
$c[0] = $b[3];
warn "entering xxx\n";
xxx( @c);
exit;
sub xxx {
    warn "hi.\n";
    return;
}
[delano@blackbox test]$ perl -d warnproblem.pl

Loading DB routines from perl5db.pl version 1.19
Editor support available.

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

main::(warnproblem.pl:1):	open I , "junk1";
  DB<1> c
entering xxx
hi.
	main::xxx('\x{9}margin="1";\x{a}') called at warnproblem.pl line 6
entering xxx
panic: malloc.
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