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In the first example, foobar is called on every list element, and first()'s economic magic is only applied to the defined operator. The second example demonstrates precisely the functionality I'm looking for.

Interpreting your question to mean that you want a list operator that short ciruits at teh first defined value it is passed, I think you are misinterpreting the results from both List::Util::first() & List::MoreUtils::first_value().

Both will short circuit if you test with defined (the use of grep is to demonstrate the contrast):

use List::Util qw[ first ];; use List::MoreUtils qw[ first_value ];; sub x{ say "<<<@_>>>"; return shift(); };; $x = grep{ defined( x($_) ) } 1, undef,3;; <<<1>>> Use of uninitialized value in join or string at (eval 17) line 1, <STD +IN> line 10. <<<>>> <<<3>>> $x = first{ defined( x( $_ ) ) } 1, undef, 3;; <<<1>>> $x = first_value{ defined( x( $_ ) ) } 1, undef, 3;; <<<1>>>

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In reply to Re: List::MoreUtils::first_value() question by BrowserUk
in thread List::MoreUtils::first_value() question by tqisjim

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