DOKK / manpages / debian 10 / libdata-dumper-concise-perl / Devel::Dwarn.3pm.en
Devel::Dwarn(3pm) User Contributed Perl Documentation Devel::Dwarn(3pm)

Devel::Dwarn - Combine warns and Data::Dumper::Concise

  use Devel::Dwarn;
  return Dwarn some_call(...)

is equivalent to:

  use Data::Dumper::Concise;
  if (wantarray) {
     my @return = some_call(...);
     warn Dumper(@return);
     return @return;
  } else {
     my $return = some_call(...);
     warn Dumper($return);
     return $return;
  }

but shorter. If you need to force scalar context on the value,

  use Devel::Dwarn;
  return DwarnS some_call(...)

is equivalent to:

  use Data::Dumper::Concise;
  my $return = some_call(...);
  warn Dumper($return);
  return $return;

If you need to force list context on the value,

  use Devel::Dwarn;
  return DwarnL some_call(...)

is equivalent to:

  use Data::Dumper::Concise;
  my @return = some_call(...);
  warn Dumper(@return);
  return @return;

If you want to label your output, try DwarnN

  use Devel::Dwarn;
  return DwarnN $foo

is equivalent to:

  use Data::Dumper::Concise;
  my @return = some_call(...);
  warn '$foo => ' . Dumper(@return);
  return @return;

If you want to output a reference returned by a method easily, try $Dwarn

 $foo->bar->{baz}->$Dwarn

is equivalent to:

  my $return = $foo->bar->{baz};
  warn Dumper($return);
  return $return;

If you want to immediately die after outputting the data structure, every Dwarn subroutine has a paired Ddie version, so just replace the warn with die. For example:

 DdieL 'foo', { bar => 'baz' };

Instead of always just doing:

  use Devel::Dwarn;
  Dwarn ...

We tend to do:

  perl -MDevel::Dwarn foo.pl

(and then in the perl code:)

  ::Dwarn ...

That way, if you leave them in and run without the "use Devel::Dwarn" the program will fail to compile and you are less likely to check it in by accident. Furthmore it allows that much less friction to add debug messages.

One trick which is useful when doing method chaining is the following:

  my $foo = Bar->new;
  $foo->bar->baz->Devel::Dwarn::DwarnS->biff;

which is the same as:

  my $foo = Bar->new;
  (DwarnS $foo->bar->baz)->biff;

This module is really just a shortcut for Data::Dumper::Concise::Sugar, check it out for more complete documentation.

2017-11-03 perl v5.26.1