The quotes are optional on barewords used as hash elements.
$hash{key} is the same as $hash{'key'}
$hash{shift} is the same as $hash{'shift'}
$hash{K} is the same as $hash{'K'}

Use
$hash{K()},
$hash{&K},
$hash{(K)} or
$hash{+K}
to work around the autoquoting.

Update: I thought I'd add a link to the relevant documentation, but I can't find documentation on this. perldata mentioned the auto-quoting property of =>, but not of the hash index.

In reply to Re: using constants by ikegami
in thread using constants by Hena

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