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};

[download]

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

Being right, does not endow the right to be rude; politeness costs nothing.
Being unknowing, is not the same as being stupid.
Expressing a contrary opinion, whether to the individual or the group, is more often a sign of deeper thought than of cantankerous belligerence.
Do not mistake your goals as the only goals; your opinion as the only opinion; your confidence as correctness. Saying you know better is not the same as explaining you know better.

In reply to Re^2: hash slice by dragonchild
in thread hash slice by pglenski

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