Hint implies that it's already solvable.

Thanks for the comments, and I did think about it - but I think I want to keep the "trick question" aspect of the node for now ;-)

Also thank you for your other replies, that's certainly getting pretty tricky with the parsing!

Some people want debug functions to disappear without footprint in production.

Like with Smart::Comments but without source filter.

Try to find a way where changing the prototype of a function &dmp will turn the call to a no op.

Your bar /#(\w+)/, @a; is already quite close, but it's still involving a division. :)

Isn't this sufficiently clear?

use constant DEBUG => 0;
use Data::Dumper;

# ...

warn Dumper($myvar) if DEBUG;
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Or PerX::Assert.

> Isn't this sufficiently clear?

> ...

> warn Dumper($myvar) if DEBUG;

clear but unnecessarily verbose.

Cheers Rolf
_{(addicted to the Perl Programming Language and ☆☆☆☆ :)
Je suis Charlie!}

an example avoiding a sub-call, unfortunately the division in void context is not optimized away.

use warnings;
use strict;
use B::Deparse;
use Data::Dump;


use constant DEBUG =>1;

BEGIN {
   unless (DEBUG) {
      *dmp = sub() {
         1;
      }
   } else {
      *dmp = sub($;@){
         shift;
         dd \@_;
      }
   }
}



sub test {
   #$_="#";
   my @a=1..3;
   dmp/#/,
     @a;
}

test();

warn "DEBUG = ",DEBUG,"\n";

print B::Deparse->new()->coderef2text(\&test);
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OUTPUT

DEBUG = 0
{
    use warnings;
    use strict;
    my(@a) = 1..3;
    1 / @a;
}
[download]

Use of uninitialized value $_ in pattern match (m//) at ... line 27.
DEBUG = 1
[1, 2, 3]
{
    use warnings;
    use strict;
    my(@a) = 1..3;
    dmp /#/, @a;
}
[download]

and the warning will create runtime overhead, too :/

update

But I think a little overhead is acceptable when debugging.

another edge case are empty arrays causing a division by zero...

update:

fixed minor bug

Cheers Rolf
_{(addicted to the Perl Programming Language and ☆☆☆☆ :)
Je suis Charlie!}

Update: Sorry haukex, the spoilers did not work when I first tried to click on them. Now that I can see them, I understand your point.