$ perl -d -e 1

Loading DB routines from perl5db.pl version 1.33
Editor support available.

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

main::(-e:1):	1
  DB<1> pwd
/Users/ken/tmp
  DB<2> date
Sun  9 Sep 2012 18:12:43 EST
  DB<3> date "%Y-%m-%d"
date: illegal time format
usage: date [-jnu] [-d dst] [-r seconds] [-t west] [-v[+|-]val[ymwdHMS]] ... 
            [-f fmt date | [[[mm]dd]HH]MM[[cc]yy][.ss]] [+format]

  DB<4> date "+%Y-%m-%d"
2012-09-09
  DB<5> ls -l
total 30824
...
drwxr-xr-x  7 ken  staff      238 14 Jun 20:23 zip_test
  DB<6> ps -ef
  UID   PID  PPID   C STIME   TTY           TIME CMD
  ...
  501 74528 74527   0 23Aug12 ttys007    0:00.04 -bash
  DB<7> q
$