in reply to Bitten by the || bug

For hack value, here is an expressive version:

sub also_correct {
    @{ ( map { @$_ ? $_ : [ list1() ] } [ list0() ] )[0] }
}

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(For some reason @{} executes its expression in void scalar context, which necessitates the ()[0] gymnastics to force the correct context on map, which would otherwise return 1. That cost me some time to track down, because I was testing on the shell in one-liners with no strict. In retrospect that was stupid, considering I was testing code with references.)

This is the list-context equivalent of list0() || list1() and has the same short-circuiting behaviour as ||.

Makeshifts last the longest.

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Re^2: Bitten by the || bug (@{})
by tye (Sage) on Feb 20, 2006 at 16:53 UTC

    s/void/scalar/, as should be expected since @{} wants a reference to an array, not a list of anything.

    - tye        

[reply]

      So it is scalar context. (Thanks for the correction on wantarray.)

      By way of an explanation: I misremembered the issue I had in mind. What I was thinking of is that the scalar reference-taking operator \ evaluates its argument in list context. This came up in discussion of the (ab)use of @{[]} or ${\()} constructs to put code inside here-docs.

      Makeshifts last the longest.

[reply]
[d/l]
[select]
      $ perl -le'print @{warn wantarray ? 1 : defined wantarray ? 0 : "undef
+"}'
undef at -e line 1.

      [download]

      Nope, void context.

      Makeshifts last the longest.

[reply]
[d/l]

        You've misused wantarray. It tells the context in which the current subroutine was called, not in what context wantarray was called. 

         > perl
sub context {
    warn
        !defined wantarray
            ? "void" :
        wantarray ? "list" : "scalar",
        $/;
}
@{context()};
<EOF>
scalar

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        - tye        

[reply]
[d/l]

In Section Meditations