I ran the code on my box, Windows XP with Activestate Perl 5.8.8 and I did not get that error. 
#!/usr/bin/perl -w
use strict;
use Data::Dump qw(dump);

my @keys = qw{ a b c d };
my %hash = map { $_++ } @keys;

warn "Dump " . dump( %hash ) . "\n";

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#!/usr/bin/perl -w
use strict;
use Data::Dump qw(dump);

my @keys = qw{ a b c d };
my %hash = ();
for (@keys) {
    $hash{$_}++;
}
warn "Dump " . dump( %hash ) . "\n";

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what I did get was, 
Dump ("c", "d", "a", "b") # first script
Dump ("a", 1, "c", 1, "b", 1, "d", 1) # second script

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Neither answer seems to be exactly what you would I want, I think.

How about telling us what you are trying to do and see if we can address that issue?

In reply to Re: Hash assignments using map by Herkum
in thread Hash assignments using map by njcodewarrior

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