wilber:/usr/src/perl-5.8.8$ gdb /usr/bin/debugperl 
GNU gdb 6.4-debian
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This GDB was configured as "x86_64-linux-gnu"...Using host libthread_db library "/lib/libthread_db.so.1".

(gdb) run -dle '$x=1;print\$x;0'
Starting program: /usr/bin/debugperl -dle '$x=1;print\$x;0'
[Thread debugging using libthread_db enabled]
[New Thread 46912504641232 (LWP 21378)]

Loading DB routines from perl5db.pl version 1.28
Editor support available.

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

main::(-e:1):   $x=1;print\$x;0
  DB<1> n
main::(-e:1):   $x=1;print\$x;0
  DB<1> 
SCALAR(0x71bd50)
main::(-e:1):   $x=1;print\$x;0
  DB<1> 
Program received signal SIGINT, Interrupt.
[Switching to Thread 46912504641232 (LWP 21378)]
0x00002aaaaae54162 in __read_nocancel () from /lib/libpthread.so.0
(gdb) p Perl_Iorigenviron_ptr
$1 = {char ***(PerlInterpreter *)} 0x57c780 <Perl_Iorigenviron_ptr>