NAME
   Sub::StopCalls - stop sub calls (make it a constant)

SYNOPSIS
       my $i = 0;

       sub boo {
           return foo();
       }
       sub foo {
           $i++;
           return Sub::StopCalls::stop();
       }

       print "$i\n"; # 0
       boo();
       print "$i\n"; # 1
       boo();
       print "$i\n"; # 1

DESCRIPTION
   Basicly you can do the following in a function to mean "Hey, You! You,
   who called me, stop calling me, I will always return the same result":

       return Sub::StopCalls::stop( @result );

   Still no idea how to use? Ok, here some use cases:

USE CASES
 conditional constants
   Classic "if DEBUG" thing:

       sub debug {
           return Sub::StopCalls::stop() unless $ENV{'MY_APP_DEBUG'};
           ...
       }

   Or logger:

       package My::Logger;
       sub warn {
           return Sub::StopCalls::stop() if $self->{max_level} < LEVEL_WARN;
           ...
       }

 accessors to singletons
       package MyApp;

       my $system;
       sub system {
           $system ||= do {
               ... init system object ...
           };
           return Sub::StopCalls::stop( $system );
       }

 hooks, triggers and callbacks
       sub trigger {
           my $self = shift;
           my @triggers = $self->find_triggers(caller);
           return Sub::StopCalls::stop() unless @triggers;

           ...
       }

FUNCTIONS
 stop
   Does the job. Replaces call on upper level with whatever is passed into
   the function. Expected usage:

       return Sub::StopCalls::stop(...) if ...;

   Some details

  context
   Result depends on context of the call that is replaced. Nothing special
   about void or array context, however, in scalar context if more than one
   argument passed into the function then number of elements returned:

       # replaces with undef
       sub foo { return Sub::StopCalls::stop(); }
       # replaces with 'const'
       sub foo { return Sub::StopCalls::stop( 'const' ); }

       # replaces with number of element in @a,
       # but only if @a > 1, otherwise first element or undef
       return Sub::StopCalls::stop( @a );

  arguments
   Arguments of the replaced call also "stopped", for example:

       for (1..10) {
           function_that_stops_calls( other(...) );
       }

   "other(...)" called only once. Second iteration just jumps over.

   It's good in theory, but in some situations it can result in bugs.

  threads
   This module is not thread-safe at the moment.

AUTHOR
   Ruslan Zakirov <[email protected]>

LICENSE
   Under the same terms as perl itself.