NAME
    Exception::Base - Lightweight exceptions

SYNOPSIS
      # Use module and create needed exceptions
      use Exception::Base
         'Exception::Runtime',              # create new module
         'Exception::System',               # load existing module
         'Exception::IO',          => {
             isa => 'Exception::System' },  # create new based on existing
         'Exception::FileNotFound' => {
             isa => 'Exception::IO',        # create new based on previous
             message => 'File not found',   # override default message
             has => [ 'filename' ],         # define new rw attribute
             string_attributes => [ 'message', 'filename' ],
         };                                 # output message and filename

      # eval is used as "try" block
      eval {
        open my $file, '/etc/passwd'
          or Exception::FileNotFound->throw(
                message=>'Something wrong',
                filename=>'/etc/passwd');
      };
      # syntax for Perl >= 5.10
      use feature 'switch';
      if ($@) {
        given (my $e = Exception::Base->catch) {
          when ($e->isa('Exception::IO')) { warn "IO problem"; }
          when ($e->isa('Exception::Eval')) { warn "eval died"; }
          when ($e->isa('Exception::Runtime')) { warn "some runtime was caught"; }
          when ($e->matches({value=>9})) { warn "something happened"; }
          when ($e->matches(qr/^Error/)) { warn "some error based on regex"; }
          default { $e->throw; } # rethrow the exception
        }
      }
      # standard syntax for older Perl
      if ($@) {
        my $e = Exception::Base->catch;   # convert $@ into exception
        if ($e->isa('Exception::IO')) { warn "IO problem"; }
        elsif ($e->isa('Exception::Eval')) { warn "eval died"; }
        elsif ($e->isa('Exception::Runtime')) { warn "some runtime was caught"; }
        elsif ($e->matches({value=>9})) { warn "something happened"; }
        elsif ($e->matches(qr/^Error/)) { warn "some error based on regex"; }
        else { $e->throw; } # rethrow the exception
      }

      # $@ has to be recovered ASAP!
      eval { die "this die will be caught" };
      my $e = Exception::Base->catch;
      eval { die "this die will be ignored" };
      if ($e) {
         (...)
      }

      # the exception can be thrown later
      my $e = Exception::Base->new;
      # (...)
      $e->throw;

      # ignore our package in stack trace
      package My::Package;
      use Exception::Base '+ignore_package' => __PACKAGE__;

      # define new exception in separate module
      package Exception::My;
      use Exception::Base (__PACKAGE__) => {
          has => ['myattr'],
      };

      # run Perl with changed verbosity for debugging purposes
      $ perl -MException::Base=verbosity,4 script.pl

DESCRIPTION
    This class implements a fully OO exception mechanism similar to
    Exception::Class or Class::Throwable. It provides a simple interface
    allowing programmers to declare exception classes. These classes can be
    thrown and caught. Each uncaught exception prints full stack trace if
    the default verbosity is uppered for debugging purposes.

    The features of `Exception::Base':

    * fast implementation of the exception class

    * fully OO without closures and source code filtering

    * does not mess with `$SIG{__DIE__}' and `$SIG{__WARN__}'

    * no external run-time modules dependencies, requires core Perl modules
      only

    * the default behavior of exception class can be changed globally or
      just for the thrown exception

    * matching the exception by class, message or other attributes

    * matching with string, regex or closure function

    * creating automatically the derived exception classes (perlfunc
      interface)

    * easly expendable, see Exception::System class for example

    * prints just an error message or dumps full stack trace

    * can propagate (rethrow) an exception

    * can ignore some packages for stack trace output

    * some defaults (i.e. verbosity) can be different for different
      exceptions

AUTHOR
    Piotr Roszatycki <dexter@cpan.org>

LICENSE
    Copyright (c) 2007, 2008, 2009 by Piotr Roszatycki <dexter@cpan.org>.

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

    See http://www.perl.com/perl/misc/Artistic.html

