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Semaphore Readers Writers Pattern or Light switch

Build Status License


use Semaphore::ReadersWriters;

my Semaphore::ReadersWriters $rw .= new;
my $shared-var = 10;

# After creating threads ...
# Some writer thread
$rw.writer( 'shv', {$shared-var += 2});

# Some reader thread
say 'Shared var is ', $rw.reader( 'shv', {$shared-var;});


  • Implement other variants of this pattern.
    • Readers priority variant.
    • No writer starvation variant.
    • Document return value restrictions. Only items, no List.


See semantic versioning. Please note point 4. on that page: Major version zero (0.y.z) is for initial development. Anything may change at any time. The public API should not be considered stable.

  • 0.2.5 Changed last method into check-mutex-names() to test for more than one name.
  • 0.2.4 Added convenience method check-mutex-name().
  • 0.2.3
    • add-mutex-names throws an exception when keys are reused
  • 0.2.2
    • Added $.debug to show messages about the actions. This will be deprecated later when I am confident enough that everything works well enaugh.
  • 0.2.1
    • Removed debugging texts to publish class
  • 0.2.0
    • Documentation
    • Bugfixes, hangups caused by overuse of same semaphores. Added more semaphores per critical section.
    • Preparations for other variations of this pattern
  • 0.1.0 First tests
  • 0.0.1 Setup


Released under Artistic License 2.0.


Marcel Timmerman


MARTIMM on github