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FAQ 4.56 What happens if I add or remove keys from a hash while iterating over it?

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FAQ 4.56 What happens if I add or remove keys from a hash while iterating over it? PerlFAQ Server 02-28-2008
Posted by PerlFAQ Server on February 28, 2008, 3:03 pm
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This is an excerpt from the latest version perlfaq4.pod, which
comes with the standard Perl distribution. These postings aim to
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to review and update the answers. The latest version of the complete
perlfaq is at http://faq.perl.org .

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4.56: What happens if I add or remove keys from a hash while iterating over it?

(contributed by brian d foy)

The easy answer is "Don't do that!"

If you iterate through the hash with each(), you can delete the key most
recently returned without worrying about it. If you delete or add other
keys, the iterator may skip or double up on them since perl may
rearrange the hash table. See the entry for "each()" in perlfunc.



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