in reply to Re: hash slice
in thread hash slice

Applying undef to a hash slice relies on undocumented behavior, . . .

It's not undocumented behavior. It's just behavior that's documented in a different place, unrelated to hashslices. Basically, undef is a keyword that takes an array. @hsh{@ary} evaluates to an array. But, to do that, Perl needs to autovivify all the slots in the hash in order to return the values. Heck, anything that takes a list will do.

undef @hsh{@ary}; chomp @hsh{@ary}; chop @hsh{@ary}; map $_, @hsh{@ary}; 1 foreach @hsh{@ary};

Those will all do the trick. The undef is a no-op to provide something that requires evaluation of a list.

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