(gdb) run -e 'sub foo { caller(0) }; *bar = *foo; my @l=bar()'
...
Breakpoint 2, Perl_pp_caller (my_perl=0x804c008) at pp_ctl.c:1567
1567        if (MAXARG)
...
(stepping over 'register I32 cxix = dopoptosub(cxstack_ix);')
...
(gdb) print ccstack[1].cx_u.cx_blk.blk_u.blku_sub.cv.sv_any.xcv_gv.sv_any[0]
$7 = {xnv_nv = 0, xpv_cur = 0, xpv_len = 0, xiv_u = {xivu_iv = 0, xivu_uv = 0, 
    xivu_p1 = 0x0}, xmg_magic = 0x80540ec, xmg_stash = 0x0, xgv_gp = 0x80540b4, 
  xgv_name = 0x805410c "foo", xgv_namelen = 3, xgv_stash = 0x804cb4c, 
  xgv_flags = 10 '\n'}
(gdb) print ccstack[1].cx_u.cx_blk.blk_u.blku_sub.cv.sv_any.xcv_gv.sv_any[1]
$8 = {xnv_nv = 0, xpv_cur = 0, xpv_len = 0, xiv_u = {xivu_iv = 0, xivu_uv = 0, 
    xivu_p1 = 0x0}, xmg_magic = 0x806f244, xmg_stash = 0x0, xgv_gp = 0x80540b4, 
  xgv_name = 0x806f264 "bar", xgv_namelen = 3, xgv_stash = 0x804cb4c, 
  xgv_flags = 10 '\n'}