All I want access to is the keys...

my @keys = qw{ a b c d };
my %hash = map { $_,1 } @keys;
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In the loop

my %hash;
foreach ( @keys ) {
    $hash{$_}++;
}
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you are also using two variables - in a shortcut:

1. you create a new hash slot with key $_
2. you increment (the previously undefined) value for that key

So, it's the same thing with keys and values here. With map iterating over an array of keys, you must provide a value to have pairs to be stored as (key,value) in a hash.

_($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}