• You can use warn...

  $i++ and warn;
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  To see more about warn.. use perldoc -f warn

  Note that if you pass arguments to warn, and it ends with a newline char, it won't show line number.

• Or using __LINE__ ...

  $i++ and printf "this is line %s\n", __LINE__;
  # or..
  $i++ and print "this is line ". __LINE__ . "\n";
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• You could also use caller (perldoc -f caller).

  $i++ and line();
  
  sub line { printf STDERR "now executing line %s\n", (caller)[2] }
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• Or use the perl debugger

What I would be asking here though.. is why?

I find that more important than telling myself what line I am executing is telling myself *what* is happening.

Perl is pretty freaking nice about telling you where things went ape- unless the code is all messed up. You know, whenever you use die().. You get told what program and where... This is way cool. Usually unless you tell perl to lie, or to give stupid output, it's very nice about finding what's up. This as opposed to stuff like php, which is the devil.

If you're using this because you have a large program that may screw up in many places... Use Carp.. Especially Carp::cluck().. which doesn't kill your program.. but tells you what happened all the way back... (man Carp)