From the documentation for map:

Evaluates BLOCK or EXPR in list context, so each element of LIST may produce zero, one, or more elements in the returned value.

use strict;
use warnings;
use v5.12;

my @array = map{ wantarray() } 0 .. 1;

my @rv = test_context();

sub test_context {
    wantarray();
}

print "\@array = map: sub block is evaluated in ";
if( defined( $array[0] ) ) {
    say $array[0]? "list context" : "scalar context";
} else {
    say "void context";
}

print "\@rv = test_context(): sub evaluated in ";
if( defined( $rv[0] ) ) {
    say $rv[0] ? "list context" : "scalar context";
} else {
    say "void context";
}

[download]

And the output is...

@array = map: sub block is evaluated in void context
@rv = test_context(): sub evaluated in list context

[download]

wantarray returns undef in void context.

What is going on here?


Dave

In reply to Is map's sub block really being evaluated in list context? wantarray() returns undef.. by davido

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