App-Dex

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  =head2 C<< run3($cmd, $stdin, $stdout, $stderr, \%options) >>
  
  All parameters after C<$cmd> are optional.
  
  The parameters C<$stdin>, C<$stdout> and C<$stderr> indicate how the child's
  corresponding filehandle (C<STDIN>, C<STDOUT> and C<STDERR>, resp.) will be
  redirected.  Because the redirects come last, this allows C<STDOUT> and
  C<STDERR> to default to the parent's by just not specifying them -- a common
  use case.
  
  C<run3> throws an exception if the wrapped C<system> call returned -1 or
  anything went wrong with C<run3>'s processing of filehandles.  Otherwise it
  returns true.  It leaves C<$?> intact for inspection of exit and wait status.
  
  Note that a true return value from C<run3> doesn't mean that the command had a
  successful exit code. Hence you should always check C<$?>.
  
  See L</%options> for an option to handle the case of C<system> returning -1
  yourself.
  
  =head3 C<$cmd>

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  If their value is true then the corresponding parameter C<$stdout> or
  C<$stderr>, resp., will append the child's output to the existing "contents" of
  the redirector. This only makes sense if the redirector is a simple scalar (the
  corresponding file is opened in append mode), a SCALAR reference (the output is
  appended to the previous contents of the string) or an ARRAY reference (the
  output is C<push>ed onto the previous contents of the array).
  
  =item C<return_if_system_error>
  
  If this is true C<run3> does B<not> throw an exception if C<system> returns -1
  (cf. L<perlfunc/system> for possible failure scenarios.), but returns true
  instead.  In this case C<$?> has the value -1 and C<$!> contains the errno of
  the failing C<system> call.
  
  =back
  
  =head1 HOW IT WORKS
  
  =over 4
  

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  =item *
  
  better: redirects more than one file descriptor
  
  =item *
  
  better: returns TRUE on success, FALSE on failure
  
  =item *
  
  better: throws an error if problems occur in the parent process (or the
  pre-exec child)
  
  =item *
  
  better: allows a very perlish interface to Perl data structures and subroutines
  
  =item *
  
  better: allows 1 word invocations to avoid the shell easily:
  

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  =back
  
  TODO:
  
  =over 4
  
  =item Parse Tree
  
  I would like to generate a complete parse tree, that allows you to manipulate
  the data structure and also dump it, including all whitespaces and comments.
  The spec says that this is throwaway content, but I read that many people
  wish to be able to keep the comments.
  
  =back
  
  =head2 YAML::PP::Dumper, YAML::PP::Emitter
  
  The Dumper should be able to dump strings correctly, adding quotes
  whenever a plain scalar would look like a special string, like C<true>,
  or when it contains or starts with characters that are not allowed.