What is Perl's equivalent to PHP's print_r()?


I find print_r in PHP extremely useful, but wonder if there is anything remotely equivalent in Perl?

2/17/2012 3:42:12 PM

Accepted Answer

Note @tchrist recommends Data::Dump over Data::Dumper. I wasn't aware of it, but from the looks of it, seems like it's both far easier to use and producing better looking and easier to interpret results.

Data::Dumper :

A snippet of the examples shown in the above link.

use Data::Dumper;

package Foo;
sub new {bless {'a' => 1, 'b' => sub { return "foo" }}, $_[0]};

package Fuz;                       # a weird REF-REF-SCALAR object
sub new {bless \($_ = \ 'fu\'z'), $_[0]};

package main;
$foo = Foo->new;
$fuz = Fuz->new;
$boo = [ 1, [], "abcd", \*foo,
         {1 => 'a', 023 => 'b', 0x45 => 'c'}, 
         \\"p\q\'r", $foo, $fuz];

# simple usage

$bar = eval(Dumper($boo));
print($@) if $@;
print Dumper($boo), Dumper($bar);  # pretty print (no array indices)

$Data::Dumper::Terse = 1;          # don't output names where feasible
$Data::Dumper::Indent = 0;         # turn off all pretty print
print Dumper($boo), "\n";

$Data::Dumper::Indent = 1;         # mild pretty print
print Dumper($boo);

$Data::Dumper::Indent = 3;         # pretty print with array indices
print Dumper($boo);

$Data::Dumper::Useqq = 1;          # print strings in double quotes
print Dumper($boo);
4/9/2015 5:06:07 AM

As usually with Perl, you might prefer alternative solutions to the venerable Data::Dumper:

  • Data::Dump::Streamer has a terser output than Data::Dumper, and can also serialize some data better than Data::Dumper,
  • YAML (or Yaml::Syck, or an other YAML module) generate the data in YAML, which is quite legible.

And of course with the debugger, you can display any variable with the 'x' command. I particularly like the form 'x 2 $complex_structure' where 2 (or any number) tells the debugger to display only 2 levels of nested data.

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