Log::Log4perl::Filter::Boolean - Special filter to combine the results of others

       Please contribute patches to the project on Github:

           http://github.com/mschilli/log4perl

       Send bug reports or requests for enhancements to the authors via our

       MAILING LIST (questions, bug reports, suggestions/patches): log4perl-devel@lists.sourceforge.net

       Authors (please contact them via the list above, not directly): Mike Schilli <m@perlmeister.com>, Kevin
       Goess <cpan@goess.org>

       Contributors (in alphabetical order): Ateeq Altaf, Cory Bennett, Jens Berthold, Jeremy Bopp, Hutton
       Davidson, Chris R. Donnelly, Matisse Enzer, Hugh Esco, Anthony Foiani, James FitzGibbon, Carl Franks,
       Dennis Gregorovic, Andy Grundman, Paul Harrington, Alexander Hartmaier  David Hull, Robert Jacobson,
       Jason Kohles, Jeff Macdonald, Markus Peter, Brett Rann, Peter Rabbitson, Erik Selberg, Aaron Straup Cope,
       Lars Thegler, David Viner, Mac Yang.

perl v5.36.0                                       2022-10-30                               Filter::Boolean(3pm)

       Sometimes, it's useful to combine the output of various filters to arrive at a log/no log decision. While
       Log4j, Log4perl's mother ship, chose to implement this feature as a filter chain, similar to Linux' IP
       chains, Log4perl tries a different approach.

       Typically, filter results will not need to be passed along in chains but combined in a programmatic
       manner using boolean logic. "Log if this filter says 'yes' and that filter says 'no'" is a fairly common
       requirement but hard to implement as a chain.

       "Log::Log4perl::Filter::Boolean" is a special predefined custom filter for Log4perl which combines the
       results of other custom filters in arbitrary ways, using boolean expressions:

           log4perl.logger = WARN, AppWarn, AppError

           log4perl.filter.Match1       = sub { /let this through/ }
           log4perl.filter.Match2       = sub { /and that, too/ }
           log4perl.filter.MyBoolean       = Log::Log4perl::Filter::Boolean
           log4perl.filter.MyBoolean.logic = Match1 || Match2

           log4perl.appender.Screen        = Log::Dispatch::Screen
           log4perl.appender.Screen.Filter = MyBoolean
           log4perl.appender.Screen.layout = Log::Log4perl::Layout::SimpleLayout

       "Log::Log4perl::Filter::Boolean"'s boolean expressions allow for combining different appenders by name
       using AND (&& or &), OR (|| or |) and NOT (!) as logical expressions. Parentheses are used for grouping.
       Precedence follows standard Perl. Here's a bunch of examples:

           Match1 && !Match2            # Match1 and not Match2
           !(Match1 || Match2)          # Neither Match1 nor Match2
           (Match1 && Match2) || Match3 # Both Match1 and Match2 or Match3

       Copyright 2002-2013 by Mike Schilli <m@perlmeister.com> and Kevin Goess <cpan@goess.org>.

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

       Log::Log4perl::Filter::Boolean - Special filter to combine the results of others

       Log::Log4perl::Filter, Log::Log4perl::Filter::LevelMatch, Log::Log4perl::Filter::LevelRange,
       Log::Log4perl::Filter::MDC, Log::Log4perl::Filter::StringRange

           log4perl.logger = WARN, AppWarn, AppError

           log4perl.filter.Match1       = sub { /let this through/ }
           log4perl.filter.Match2       = sub { /and that, too/ }
           log4perl.filter.MyBoolean       = Log::Log4perl::Filter::Boolean
           log4perl.filter.MyBoolean.logic = Match1 || Match2

           log4perl.appender.Screen        = Log::Dispatch::Screen
           log4perl.appender.Screen.Filter = MyBoolean
           log4perl.appender.Screen.layout = Log::Log4perl::Layout::SimpleLayout