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+# Error.pm
+#
+# Copyright (c) 1997-8 Graham Barr <gbarr@ti.com>. All rights reserved.
+# This program is free software; you can redistribute it and/or
+# modify it under the same terms as Perl itself.
+#
+# Based on my original Error.pm, and Exceptions.pm by Peter Seibel
+# <peter@weblogic.com> and adapted by Jesse Glick <jglick@sig.bsh.com>.
+#
+# but modified ***significantly***
+
+package Error;
+
+use strict;
+use warnings;
+
+use vars qw($VERSION);
+use 5.004;
+
+$VERSION = "0.17025";
+
+use overload (
+ '""' => 'stringify',
+ '0+' => 'value',
+ 'bool' => sub { return 1; },
+ 'fallback' => 1
+);
+
+$Error::Depth = 0; # Depth to pass to caller()
+$Error::Debug = 0; # Generate verbose stack traces
+@Error::STACK = (); # Clause stack for try
+$Error::THROWN = undef; # last error thrown, a workaround until die $ref works
+
+my $LAST; # Last error created
+my %ERROR; # Last error associated with package
+
+sub _throw_Error_Simple
+{
+ my $args = shift;
+ return Error::Simple->new($args->{'text'});
+}
+
+$Error::ObjectifyCallback = \&_throw_Error_Simple;
+
+
+# Exported subs are defined in Error::subs
+
+use Scalar::Util ();
+
+sub import {
+ shift;
+ my @tags = @_;
+ local $Exporter::ExportLevel = $Exporter::ExportLevel + 1;
+
+ @tags = grep {
+ if( $_ eq ':warndie' ) {
+ Error::WarnDie->import();
+ 0;
+ }
+ else {
+ 1;
+ }
+ } @tags;
+
+ Error::subs->import(@tags);
+}
+
+# I really want to use last for the name of this method, but it is a keyword
+# which prevent the syntax last Error
+
+sub prior {
+ shift; # ignore
+
+ return $LAST unless @_;
+
+ my $pkg = shift;
+ return exists $ERROR{$pkg} ? $ERROR{$pkg} : undef
+ unless ref($pkg);
+
+ my $obj = $pkg;
+ my $err = undef;
+ if($obj->isa('HASH')) {
+ $err = $obj->{'__Error__'}
+ if exists $obj->{'__Error__'};
+ }
+ elsif($obj->isa('GLOB')) {
+ $err = ${*$obj}{'__Error__'}
+ if exists ${*$obj}{'__Error__'};
+ }
+
+ $err;
+}
+
+sub flush {
+ shift; #ignore
+
+ unless (@_) {
+ $LAST = undef;
+ return;
+ }
+
+ my $pkg = shift;
+ return unless ref($pkg);
+
+ undef $ERROR{$pkg} if defined $ERROR{$pkg};
+}
+
+# Return as much information as possible about where the error
+# happened. The -stacktrace element only exists if $Error::DEBUG
+# was set when the error was created
+
+sub stacktrace {
+ my $self = shift;
+
+ return $self->{'-stacktrace'}
+ if exists $self->{'-stacktrace'};
+
+ my $text = exists $self->{'-text'} ? $self->{'-text'} : "Died";
+
+ $text .= sprintf(" at %s line %d.\n", $self->file, $self->line)
+ unless($text =~ /\n$/s);
+
+ $text;
+}
+
+
+sub associate {
+ my $err = shift;
+ my $obj = shift;
+
+ return unless ref($obj);
+
+ if($obj->isa('HASH')) {
+ $obj->{'__Error__'} = $err;
+ }
+ elsif($obj->isa('GLOB')) {
+ ${*$obj}{'__Error__'} = $err;
+ }
+ $obj = ref($obj);
+ $ERROR{ ref($obj) } = $err;
+
+ return;
+}
+
+
+sub new {
+ my $self = shift;
+ my($pkg,$file,$line) = caller($Error::Depth);
+
+ my $err = bless {
+ '-package' => $pkg,
+ '-file' => $file,
+ '-line' => $line,
+ @_
+ }, $self;
+
+ $err->associate($err->{'-object'})
+ if(exists $err->{'-object'});
+
+ # To always create a stacktrace would be very inefficient, so
+ # we only do it if $Error::Debug is set
+
+ if($Error::Debug) {
+ require Carp;
+ local $Carp::CarpLevel = $Error::Depth;
+ my $text = defined($err->{'-text'}) ? $err->{'-text'} : "Error";
+ my $trace = Carp::longmess($text);
+ # Remove try calls from the trace
+ $trace =~ s/(\n\s+\S+__ANON__[^\n]+)?\n\s+eval[^\n]+\n\s+Error::subs::try[^\n]+(?=\n)//sog;
+ $trace =~ s/(\n\s+\S+__ANON__[^\n]+)?\n\s+eval[^\n]+\n\s+Error::subs::run_clauses[^\n]+\n\s+Error::subs::try[^\n]+(?=\n)//sog;
+ $err->{'-stacktrace'} = $trace
+ }
+
+ $@ = $LAST = $ERROR{$pkg} = $err;
+}
+
+# Throw an error. this contains some very gory code.
+
+sub throw {
+ my $self = shift;
+ local $Error::Depth = $Error::Depth + 1;
+
+ # if we are not rethrow-ing then create the object to throw
+ $self = $self->new(@_) unless ref($self);
+
+ die $Error::THROWN = $self;
+}
+
+# syntactic sugar for
+#
+# die with Error( ... );
+
+sub with {
+ my $self = shift;
+ local $Error::Depth = $Error::Depth + 1;
+
+ $self->new(@_);
+}
+
+# syntactic sugar for
+#
+# record Error( ... ) and return;
+
+sub record {
+ my $self = shift;
+ local $Error::Depth = $Error::Depth + 1;
+
+ $self->new(@_);
+}
+
+# catch clause for
+#
+# try { ... } catch CLASS with { ... }
+
+sub catch {
+ my $pkg = shift;
+ my $code = shift;
+ my $clauses = shift || {};
+ my $catch = $clauses->{'catch'} ||= [];
+
+ unshift @$catch, $pkg, $code;
+
+ $clauses;
+}
+
+# Object query methods
+
+sub object {
+ my $self = shift;
+ exists $self->{'-object'} ? $self->{'-object'} : undef;
+}
+
+sub file {
+ my $self = shift;
+ exists $self->{'-file'} ? $self->{'-file'} : undef;
+}
+
+sub line {
+ my $self = shift;
+ exists $self->{'-line'} ? $self->{'-line'} : undef;
+}
+
+sub text {
+ my $self = shift;
+ exists $self->{'-text'} ? $self->{'-text'} : undef;
+}
+
+# overload methods
+
+sub stringify {
+ my $self = shift;
+ defined $self->{'-text'} ? $self->{'-text'} : "Died";
+}
+
+sub value {
+ my $self = shift;
+ exists $self->{'-value'} ? $self->{'-value'} : undef;
+}
+
+package Error::Simple;
+
+use vars qw($VERSION);
+
+$VERSION = "0.17025";
+
+@Error::Simple::ISA = qw(Error);
+
+sub new {
+ my $self = shift;
+ my $text = "" . shift;
+ my $value = shift;
+ my(@args) = ();
+
+ local $Error::Depth = $Error::Depth + 1;
+
+ @args = ( -file => $1, -line => $2)
+ if($text =~ s/\s+at\s+(\S+)\s+line\s+(\d+)(?:,\s*<[^>]*>\s+line\s+\d+)?\.?\n?$//s);
+ push(@args, '-value', 0 + $value)
+ if defined($value);
+
+ $self->SUPER::new(-text => $text, @args);
+}
+
+sub stringify {
+ my $self = shift;
+ my $text = $self->SUPER::stringify;
+ $text .= sprintf(" at %s line %d.\n", $self->file, $self->line)
+ unless($text =~ /\n$/s);
+ $text;
+}
+
+##########################################################################
+##########################################################################
+
+# Inspired by code from Jesse Glick <jglick@sig.bsh.com> and
+# Peter Seibel <peter@weblogic.com>
+
+package Error::subs;
+
+use Exporter ();
+use vars qw(@EXPORT_OK @ISA %EXPORT_TAGS);
+
+@EXPORT_OK = qw(try with finally except otherwise);
+%EXPORT_TAGS = (try => \@EXPORT_OK);
+
+@ISA = qw(Exporter);
+
+sub run_clauses ($$$\@) {
+ my($clauses,$err,$wantarray,$result) = @_;
+ my $code = undef;
+
+ $err = $Error::ObjectifyCallback->({'text' =>$err}) unless ref($err);
+
+ CATCH: {
+
+ # catch
+ my $catch;
+ if(defined($catch = $clauses->{'catch'})) {
+ my $i = 0;
+
+ CATCHLOOP:
+ for( ; $i < @$catch ; $i += 2) {
+ my $pkg = $catch->[$i];
+ unless(defined $pkg) {
+ #except
+ splice(@$catch,$i,2,$catch->[$i+1]->($err));
+ $i -= 2;
+ next CATCHLOOP;
+ }
+ elsif(Scalar::Util::blessed($err) && $err->isa($pkg)) {
+ $code = $catch->[$i+1];
+ while(1) {
+ my $more = 0;
+ local($Error::THROWN, $@);
+ my $ok = eval {
+ $@ = $err;
+ if($wantarray) {
+ @{$result} = $code->($err,\$more);
+ }
+ elsif(defined($wantarray)) {
+ @{$result} = ();
+ $result->[0] = $code->($err,\$more);
+ }
+ else {
+ $code->($err,\$more);
+ }
+ 1;
+ };
+ if( $ok ) {
+ next CATCHLOOP if $more;
+ undef $err;
+ }
+ else {
+ $err = $@ || $Error::THROWN;
+ $err = $Error::ObjectifyCallback->({'text' =>$err})
+ unless ref($err);
+ }
+ last CATCH;
+ };
+ }
+ }
+ }
+
+ # otherwise
+ my $owise;
+ if(defined($owise = $clauses->{'otherwise'})) {
+ my $code = $clauses->{'otherwise'};
+ my $more = 0;
+ local($Error::THROWN, $@);
+ my $ok = eval {
+ $@ = $err;
+ if($wantarray) {
+ @{$result} = $code->($err,\$more);
+ }
+ elsif(defined($wantarray)) {
+ @{$result} = ();
+ $result->[0] = $code->($err,\$more);
+ }
+ else {
+ $code->($err,\$more);
+ }
+ 1;
+ };
+ if( $ok ) {
+ undef $err;
+ }
+ else {
+ $err = $@ || $Error::THROWN;
+
+ $err = $Error::ObjectifyCallback->({'text' =>$err})
+ unless ref($err);
+ }
+ }
+ }
+ $err;
+}
+
+sub try (&;$) {
+ my $try = shift;
+ my $clauses = @_ ? shift : {};
+ my $ok = 0;
+ my $err = undef;
+ my @result = ();
+
+ unshift @Error::STACK, $clauses;
+
+ my $wantarray = wantarray();
+
+ do {
+ local $Error::THROWN = undef;
+ local $@ = undef;
+
+ $ok = eval {
+ if($wantarray) {
+ @result = $try->();
+ }
+ elsif(defined $wantarray) {
+ $result[0] = $try->();
+ }
+ else {
+ $try->();
+ }
+ 1;
+ };
+
+ $err = $@ || $Error::THROWN
+ unless $ok;
+ };
+
+ shift @Error::STACK;
+
+ $err = run_clauses($clauses,$err,wantarray,@result)
+ unless($ok);
+
+ $clauses->{'finally'}->()
+ if(defined($clauses->{'finally'}));
+
+ if (defined($err))
+ {
+ if (Scalar::Util::blessed($err) && $err->can('throw'))
+ {
+ throw $err;
+ }
+ else
+ {
+ die $err;
+ }
+ }
+
+ wantarray ? @result : $result[0];
+}
+
+# Each clause adds a sub to the list of clauses. The finally clause is
+# always the last, and the otherwise clause is always added just before
+# the finally clause.
+#
+# All clauses, except the finally clause, add a sub which takes one argument
+# this argument will be the error being thrown. The sub will return a code ref
+# if that clause can handle that error, otherwise undef is returned.
+#
+# The otherwise clause adds a sub which unconditionally returns the users
+# code reference, this is why it is forced to be last.
+#
+# The catch clause is defined in Error.pm, as the syntax causes it to
+# be called as a method
+
+sub with (&;$) {
+ @_
+}
+
+sub finally (&) {
+ my $code = shift;
+ my $clauses = { 'finally' => $code };
+ $clauses;
+}
+
+# The except clause is a block which returns a hashref or a list of
+# key-value pairs, where the keys are the classes and the values are subs.
+
+sub except (&;$) {
+ my $code = shift;
+ my $clauses = shift || {};
+ my $catch = $clauses->{'catch'} ||= [];
+
+ my $sub = sub {
+ my $ref;
+ my(@array) = $code->($_[0]);
+ if(@array == 1 && ref($array[0])) {
+ $ref = $array[0];
+ $ref = [ %$ref ]
+ if(UNIVERSAL::isa($ref,'HASH'));
+ }
+ else {
+ $ref = \@array;
+ }
+ @$ref
+ };
+
+ unshift @{$catch}, undef, $sub;
+
+ $clauses;
+}
+
+sub otherwise (&;$) {
+ my $code = shift;
+ my $clauses = shift || {};
+
+ if(exists $clauses->{'otherwise'}) {
+ require Carp;
+ Carp::croak("Multiple otherwise clauses");
+ }
+
+ $clauses->{'otherwise'} = $code;
+
+ $clauses;
+}
+
+1;
+
+package Error::WarnDie;
+
+sub gen_callstack($)
+{
+ my ( $start ) = @_;
+
+ require Carp;
+ local $Carp::CarpLevel = $start;
+ my $trace = Carp::longmess("");
+ # Remove try calls from the trace
+ $trace =~ s/(\n\s+\S+__ANON__[^\n]+)?\n\s+eval[^\n]+\n\s+Error::subs::try[^\n]+(?=\n)//sog;
+ $trace =~ s/(\n\s+\S+__ANON__[^\n]+)?\n\s+eval[^\n]+\n\s+Error::subs::run_clauses[^\n]+\n\s+Error::subs::try[^\n]+(?=\n)//sog;
+ my @callstack = split( m/\n/, $trace );
+ return @callstack;
+}
+
+my $old_DIE;
+my $old_WARN;
+
+sub DEATH
+{
+ my ( $e ) = @_;
+
+ local $SIG{__DIE__} = $old_DIE if( defined $old_DIE );
+
+ die @_ if $^S;
+
+ my ( $etype, $message, $location, @callstack );
+ if ( ref($e) && $e->isa( "Error" ) ) {
+ $etype = "exception of type " . ref( $e );
+ $message = $e->text;
+ $location = $e->file . ":" . $e->line;
+ @callstack = split( m/\n/, $e->stacktrace );
+ }
+ else {
+ # Don't apply subsequent layer of message formatting
+ die $e if( $e =~ m/^\nUnhandled perl error caught at toplevel:\n\n/ );
+ $etype = "perl error";
+ my $stackdepth = 0;
+ while( caller( $stackdepth ) =~ m/^Error(?:$|::)/ ) {
+ $stackdepth++
+ }
+
+ @callstack = gen_callstack( $stackdepth + 1 );
+
+ $message = "$e";
+ chomp $message;
+
+ if ( $message =~ s/ at (.*?) line (\d+)\.$// ) {
+ $location = $1 . ":" . $2;
+ }
+ else {
+ my @caller = caller( $stackdepth );
+ $location = $caller[1] . ":" . $caller[2];
+ }
+ }
+
+ shift @callstack;
+ # Do it this way in case there are no elements; we don't print a spurious \n
+ my $callstack = join( "", map { "$_\n"} @callstack );
+
+ die "\nUnhandled $etype caught at toplevel:\n\n $message\n\nThrown from: $location\n\nFull stack trace:\n\n$callstack\n";
+}
+
+sub TAXES
+{
+ my ( $message ) = @_;
+
+ local $SIG{__WARN__} = $old_WARN if( defined $old_WARN );
+
+ $message =~ s/ at .*? line \d+\.$//;
+ chomp $message;
+
+ my @callstack = gen_callstack( 1 );
+ my $location = shift @callstack;
+
+ # $location already starts in a leading space
+ $message .= $location;
+
+ # Do it this way in case there are no elements; we don't print a spurious \n
+ my $callstack = join( "", map { "$_\n"} @callstack );
+
+ warn "$message:\n$callstack";
+}
+
+sub import
+{
+ $old_DIE = $SIG{__DIE__};
+ $old_WARN = $SIG{__WARN__};
+
+ $SIG{__DIE__} = \&DEATH;
+ $SIG{__WARN__} = \&TAXES;
+}
+
+1;
+
+__END__
+
+=head1 NAME
+
+Error - Error/exception handling in an OO-ish way
+
+=head1 WARNING
+
+Using the "Error" module is B<no longer recommended> due to the black-magical
+nature of its syntactic sugar, which often tends to break. Its maintainers
+have stopped actively writing code that uses it, and discourage people
+from doing so. See the "SEE ALSO" section below for better recommendations.
+
+=head1 SYNOPSIS
+
+ use Error qw(:try);
+
+ throw Error::Simple( "A simple error");
+
+ sub xyz {
+ ...
+ record Error::Simple("A simple error")
+ and return;
+ }
+
+ unlink($file) or throw Error::Simple("$file: $!",$!);
+
+ try {
+ do_some_stuff();
+ die "error!" if $condition;
+ throw Error::Simple "Oops!" if $other_condition;
+ }
+ catch Error::IO with {
+ my $E = shift;
+ print STDERR "File ", $E->{'-file'}, " had a problem\n";
+ }
+ except {
+ my $E = shift;
+ my $general_handler=sub {send_message $E->{-description}};
+ return {
+ UserException1 => $general_handler,
+ UserException2 => $general_handler
+ };
+ }
+ otherwise {
+ print STDERR "Well I don't know what to say\n";
+ }
+ finally {
+ close_the_garage_door_already(); # Should be reliable
+ }; # Don't forget the trailing ; or you might be surprised
+
+=head1 DESCRIPTION
+
+The C<Error> package provides two interfaces. Firstly C<Error> provides
+a procedural interface to exception handling. Secondly C<Error> is a
+base class for errors/exceptions that can either be thrown, for
+subsequent catch, or can simply be recorded.
+
+Errors in the class C<Error> should not be thrown directly, but the
+user should throw errors from a sub-class of C<Error>.
+
+=head1 PROCEDURAL INTERFACE
+
+C<Error> exports subroutines to perform exception handling. These will
+be exported if the C<:try> tag is used in the C<use> line.
+
+=over 4
+
+=item try BLOCK CLAUSES
+
+C<try> is the main subroutine called by the user. All other subroutines
+exported are clauses to the try subroutine.
+
+The BLOCK will be evaluated and, if no error is throw, try will return
+the result of the block.
+
+C<CLAUSES> are the subroutines below, which describe what to do in the
+event of an error being thrown within BLOCK.
+
+=item catch CLASS with BLOCK
+
+This clauses will cause all errors that satisfy C<$err-E<gt>isa(CLASS)>
+to be caught and handled by evaluating C<BLOCK>.
+
+C<BLOCK> will be passed two arguments. The first will be the error
+being thrown. The second is a reference to a scalar variable. If this
+variable is set by the catch block then, on return from the catch
+block, try will continue processing as if the catch block was never
+found. The error will also be available in C<$@>.
+
+To propagate the error the catch block may call C<$err-E<gt>throw>
+
+If the scalar reference by the second argument is not set, and the
+error is not thrown. Then the current try block will return with the
+result from the catch block.
+
+=item except BLOCK
+
+When C<try> is looking for a handler, if an except clause is found
+C<BLOCK> is evaluated. The return value from this block should be a
+HASHREF or a list of key-value pairs, where the keys are class names
+and the values are CODE references for the handler of errors of that
+type.
+
+=item otherwise BLOCK
+
+Catch any error by executing the code in C<BLOCK>
+
+When evaluated C<BLOCK> will be passed one argument, which will be the
+error being processed. The error will also be available in C<$@>.
+
+Only one otherwise block may be specified per try block
+
+=item finally BLOCK
+
+Execute the code in C<BLOCK> either after the code in the try block has
+successfully completed, or if the try block throws an error then
+C<BLOCK> will be executed after the handler has completed.
+
+If the handler throws an error then the error will be caught, the
+finally block will be executed and the error will be re-thrown.
+
+Only one finally block may be specified per try block
+
+=back
+
+=head1 COMPATIBILITY
+
+L<Moose> exports a keyword called C<with> which clashes with Error's. This
+example returns a prototype mismatch error:
+
+ package MyTest;
+
+ use warnings;
+ use Moose;
+ use Error qw(:try);
+
+(Thanks to C<maik.hentsche@amd.com> for the report.).
+
+=head1 CLASS INTERFACE
+
+=head2 CONSTRUCTORS
+
+The C<Error> object is implemented as a HASH. This HASH is initialized
+with the arguments that are passed to it's constructor. The elements
+that are used by, or are retrievable by the C<Error> class are listed
+below, other classes may add to these.
+
+ -file
+ -line
+ -text
+ -value
+ -object
+
+If C<-file> or C<-line> are not specified in the constructor arguments
+then these will be initialized with the file name and line number where
+the constructor was called from.
+
+If the error is associated with an object then the object should be
+passed as the C<-object> argument. This will allow the C<Error> package
+to associate the error with the object.
+
+The C<Error> package remembers the last error created, and also the
+last error associated with a package. This could either be the last
+error created by a sub in that package, or the last error which passed
+an object blessed into that package as the C<-object> argument.
+
+=over 4
+
+=item Error->new()
+
+See the Error::Simple documentation.
+
+=item throw ( [ ARGS ] )
+
+Create a new C<Error> object and throw an error, which will be caught
+by a surrounding C<try> block, if there is one. Otherwise it will cause
+the program to exit.
+
+C<throw> may also be called on an existing error to re-throw it.
+
+=item with ( [ ARGS ] )
+
+Create a new C<Error> object and returns it. This is defined for
+syntactic sugar, eg
+
+ die with Some::Error ( ... );
+
+=item record ( [ ARGS ] )
+
+Create a new C<Error> object and returns it. This is defined for
+syntactic sugar, eg
+
+ record Some::Error ( ... )
+ and return;
+
+=back
+
+=head2 STATIC METHODS
+
+=over 4
+
+=item prior ( [ PACKAGE ] )
+
+Return the last error created, or the last error associated with
+C<PACKAGE>
+
+=item flush ( [ PACKAGE ] )
+
+Flush the last error created, or the last error associated with
+C<PACKAGE>.It is necessary to clear the error stack before exiting the
+package or uncaught errors generated using C<record> will be reported.
+
+ $Error->flush;
+
+=cut
+
+=back
+
+=head2 OBJECT METHODS
+
+=over 4
+
+=item stacktrace
+
+If the variable C<$Error::Debug> was non-zero when the error was
+created, then C<stacktrace> returns a string created by calling
+C<Carp::longmess>. If the variable was zero the C<stacktrace> returns
+the text of the error appended with the filename and line number of
+where the error was created, providing the text does not end with a
+newline.
+
+=item object
+
+The object this error was associated with
+
+=item file
+
+The file where the constructor of this error was called from
+
+=item line
+
+The line where the constructor of this error was called from
+
+=item text
+
+The text of the error
+
+=item $err->associate($obj)
+
+Associates an error with an object to allow error propagation. I.e:
+
+ $ber->encode(...) or
+ return Error->prior($ber)->associate($ldap);
+
+=back
+
+=head2 OVERLOAD METHODS
+
+=over 4
+
+=item stringify
+
+A method that converts the object into a string. This method may simply
+return the same as the C<text> method, or it may append more
+information. For example the file name and line number.
+
+By default this method returns the C<-text> argument that was passed to
+the constructor, or the string C<"Died"> if none was given.
+
+=item value
+
+A method that will return a value that can be associated with the
+error. For example if an error was created due to the failure of a
+system call, then this may return the numeric value of C<$!> at the
+time.
+
+By default this method returns the C<-value> argument that was passed
+to the constructor.
+
+=back
+
+=head1 PRE-DEFINED ERROR CLASSES
+
+=head2 Error::Simple
+
+This class can be used to hold simple error strings and values. It's
+constructor takes two arguments. The first is a text value, the second
+is a numeric value. These values are what will be returned by the
+overload methods.
+
+If the text value ends with C<at file line 1> as $@ strings do, then
+this information will be used to set the C<-file> and C<-line> arguments
+of the error object.
+
+This class is used internally if an eval'd block die's with an error
+that is a plain string. (Unless C<$Error::ObjectifyCallback> is modified)
+
+
+=head1 $Error::ObjectifyCallback
+
+This variable holds a reference to a subroutine that converts errors that
+are plain strings to objects. It is used by Error.pm to convert textual
+errors to objects, and can be overridden by the user.
+
+It accepts a single argument which is a hash reference to named parameters.
+Currently the only named parameter passed is C<'text'> which is the text
+of the error, but others may be available in the future.
+
+For example the following code will cause Error.pm to throw objects of the
+class MyError::Bar by default:
+
+ sub throw_MyError_Bar
+ {
+ my $args = shift;
+ my $err = MyError::Bar->new();
+ $err->{'MyBarText'} = $args->{'text'};
+ return $err;
+ }
+
+ {
+ local $Error::ObjectifyCallback = \&throw_MyError_Bar;
+
+ # Error handling here.
+ }
+
+=cut
+
+=head1 MESSAGE HANDLERS
+
+C<Error> also provides handlers to extend the output of the C<warn()> perl
+function, and to handle the printing of a thrown C<Error> that is not caught
+or otherwise handled. These are not installed by default, but are requested
+using the C<:warndie> tag in the C<use> line.
+
+ use Error qw( :warndie );
+
+These new error handlers are installed in C<$SIG{__WARN__}> and
+C<$SIG{__DIE__}>. If these handlers are already defined when the tag is
+imported, the old values are stored, and used during the new code. Thus, to
+arrange for custom handling of warnings and errors, you will need to perform
+something like the following:
+
+ BEGIN {
+ $SIG{__WARN__} = sub {
+ print STDERR "My special warning handler: $_[0]"
+ };
+ }
+
+ use Error qw( :warndie );
+
+Note that setting C<$SIG{__WARN__}> after the C<:warndie> tag has been
+imported will overwrite the handler that C<Error> provides. If this cannot be
+avoided, then the tag can be explicitly C<import>ed later
+
+ use Error;
+
+ $SIG{__WARN__} = ...;
+
+ import Error qw( :warndie );
+
+=head2 EXAMPLE
+
+The C<__DIE__> handler turns messages such as
+
+ Can't call method "foo" on an undefined value at examples/warndie.pl line 16.
+
+into
+
+ Unhandled perl error caught at toplevel:
+
+ Can't call method "foo" on an undefined value
+
+ Thrown from: examples/warndie.pl:16
+
+ Full stack trace:
+
+ main::inner('undef') called at examples/warndie.pl line 20
+ main::outer('undef') called at examples/warndie.pl line 23
+
+=cut
+
+=head1 SEE ALSO
+
+See L<Exception::Class> for a different module providing Object-Oriented
+exception handling, along with a convenient syntax for declaring hierarchies
+for them. It doesn't provide Error's syntactic sugar of C<try { ... }>,
+C<catch { ... }>, etc. which may be a good thing or a bad thing based
+on what you want. (Because Error's syntactic sugar tends to break.)
+
+L<Error::Exception> aims to combine L<Error> and L<Exception::Class>
+"with correct stringification".
+
+L<TryCatch> and L<Try::Tiny> are similar in concept to Error.pm only providing
+a syntax that hopefully breaks less.
+
+=head1 KNOWN BUGS
+
+None, but that does not mean there are not any.
+
+=head1 AUTHORS
+
+Graham Barr <gbarr@pobox.com>
+
+The code that inspired me to write this was originally written by
+Peter Seibel <peter@weblogic.com> and adapted by Jesse Glick
+<jglick@sig.bsh.com>.
+
+C<:warndie> handlers added by Paul Evans <leonerd@leonerd.org.uk>
+
+=head1 MAINTAINER
+
+Shlomi Fish, L<http://www.shlomifish.org/> .
+
+=head1 PAST MAINTAINERS
+
+Arun Kumar U <u_arunkumar@yahoo.com>
+
+=head1 COPYRIGHT
+
+Copyright (c) 1997-8 Graham Barr. All rights reserved.
+This program is free software; you can redistribute it and/or modify it
+under the same terms as Perl itself.
+
+=cut
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