Author image Piotr Roszatycki


Exception::Warning - Convert simple warn into real exception object


  # Convert warn into exception and throw it immediately
  use Exception::Warning '%SIG' => 'die';
  eval { warn "Boom!"; };
  print ref $@;        # "Exception::Warning"
  print $@->warning;   # "Boom!"

  # Convert warn into exception without die
  use Exception::Warning '%SIG' => 'warn', verbosity => 4;
  warn "Boom!";   # dumps full stack trace

  # Can be used in local scope only
  use Exception::Warning;
      local $SIG{__WARN__} = \&Exception::Warning::__WARN__;
      warn "Boom!";   # warn via exception
  warn "Boom!";       # standard warn

  # Run Perl with verbose warnings
  $ perl -MException::Warning=%SIG,warn,verbosity=>3

  # Run Perl which dies on first warning
  $ perl -MException::Warning=%SIG,die,verbosity=>3

  # Run Perl which ignores any warnings
  $ perl -MException::Warning=%SIG,warn,verbosity=>0

  # Debugging with increased verbosity
  $ perl -MException::Warning=:debug


This class extends standard Exception::Base and converts warning into real exception object. The warning message is stored in warning attribute.



ATTRS : HashRef

Declaration of class attributes as reference to hash.

See Exception::Base for details.


This class provides new attributes. See Exception::Base for other descriptions.

warning : Str {ro}

Contains the message which is set by $SIG{__WARN__} hook.

message : Str = "Unknown warning"

Contains the message of the exception. This class overrides the default value from Exception::Base class.

string_attributes : ArrayRef[Str] = ["message", "warning"]

Meta-attribute contains the format of string representation of exception object. This class overrides the default value from Exception::Base class.

default_attribute : Str = "warning"

Meta-attribute contains the name of the default attribute. This class overrides the default value from Exception::Base class.


use Exception::Warning '%SIG';
use Exception::Warning '%SIG' => 'warn';

Changes $SIG{__WARN__} hook to Exception::Warning::__WARN__.

use Exception::Warning '%SIG' => 'die';

Changes $SIG{__WARN__} hook to Exception::Warning::__DIE__ function.

use Exception::Warning ':debug';

Changes $SIG{__WARN__} hook to Exception::Warning::__WARN__ and sets verbosity level to 4 (maximum).

no Exception::Warning '%SIG';

Undefines $SIG{__DIE__} hook.


The Exception::Warning module can change $SIG{__WARN__} hook. It costs a speed for simple warn operation. It was tested against unhooked warn.

  | Module                              |         run/s |
  | undef $SIG{__WARN__}                |      276243/s |
  | $SIG{__WARN__} = sub { }            |      188215/s |
  | Exception::Warning '%SIG'           |        1997/s |
  | Exception::Warning '%SIG', verb.=>0 |       26934/s |

It means that Exception::Warning is significally slower than simple warn. It is usually used only for debugging purposes, so it shouldn't be an important problem.




If you find the bug or want to implement new features, please report it at


Piotr Roszatycki <>


Copyright (C) 2008, 2009 by Piotr Roszatycki <>.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.