A require is a Test2 module that will skip the current test if a condition is not met.
These are useful if you have tests that require other modules, or should only be run on specific platforms.
Skip the test unless the AUTHOR_TESTING environment variable is set.
Skip the test unless the specified environment variable is set.
Only run tests on systems that can fork for real.
Checking yourself is not that hard, but does your intentions are not as clear: Did you actually want to run only when real forking is available, or did you intend to include emulated fork?
Only run the test if the required module (and optionally version) is installed.
Skip the test unless the necessary version of perl is installed.
Only run tests on perls that have threading enabled.
Checking for threads yourself is not as trivial as it may sound: