perl で sh -x みたいなことをするには

% perl -d a.pl

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::(a.pl:19):        my ($l_debug) = (0);
  DB<1> t
Trace = on
  DB<1> r
main::(a.pl:36):        & main;
main::main(a.pl:26):            my %options = (
main::main(a.pl:27):                    "debug"         =>      \$l_debug
main::main(a.pl:28):            );
main::main(a.pl:30):            print ("a\n");
a
main::main(a.pl:32):            exit (0);
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>