"Assertion" is the wrong word here because unless you do gymnastics the code block has no affect on whether the expression succeeds or fails. On the rare occasion that I want to use perl code in an assertion (and this never happens for "real" code) you have to use the eval block in a conditional and then use zero-width assertions to simulate a true-false.

/(? # Use the conditional construct

   (?{ perl code goes here})  # Perl code that will assert something

   (?=)  # empty positive assertion.

   |

   (?!)  # empty negative assertion

 )/x
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Why don't you use (??{ }) for that?

Makeshifts last the longest.

Huh. I wouldn't have thought to use (??{}) for that and still won't. It invokes the regex compiler which isn't necessary for the code2assert I posted. This works identically except its slower.

/(??{  # delayed regex
     $condition
         ? ''     # Nothing needed - this succeeds by default
         : '(?!)' # Failed!
 })/
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History has it that Mr Wilde's response was, "You will Harvey, you will.". So, in this case, I guess I should simply say. "I will" :)

In C  assert(true); could still be classed as an "assertion". The fact that the assertion is always true doesn't change that. perlre says

This zero-width assertion evaluate any embedded Perl code. It always s
+ucceeds,
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so 'code block assertion' as a phrase to describe (?{ ... }) makes a certain amount of sense, to me at least.

And the (??{ ... }) is described as a "postponed regular subexpression".

Both are a bit wordy, but it would be nice to have terms for them, rather than needing to constantly use the notation? Maybe CBA and PP-RE?? Just a thought.

FWIW, I tend to think of them as "RE eval" and "deferred eval", influenced in part by:

  perl -wle 'sub a { print +(caller)[1] } ""=~/(?{ a() })/'
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Hugo

That's much better than either my long-winded versions or the aweful TLA's. It also reminds us of the runtime costs.

Thanks. I'll update my lexicon:)

---

Examine what is said, not who speaks.
"Efficiency is intelligent laziness." -David Dunham
"When I'm working on a problem, I never think about beauty. I think only how to solve the problem. But when I have finished, if the solution is not beautiful, I know it is wrong." -Richard Buckminster Fuller