Trace Execution

Occasionally-asked question:
"How can I emulate the behavior of the Bourne shell -x option?"
Here's one way:

        package Devel::Trace;

        sub DB::DB {
          my ($p, $f, $l) = caller;
          my $code = \@{"::_<$f"};
          print STDERR ">> $f($l) $code->[$l]";
        }

Now perl -d:Trace sample.pl prints out:

        >> sample.pl(1) for (1 .. ($ARGV[0] || 12)) {
        >> sample.pl(2)   next unless $_ % 12;
        >> sample.pl(3)   print "";
        >> sample.pl(1) for (1 .. ($ARGV[0] || 12)) {
        (etc.)