Deda has asked for the wisdom of the Perl Monks concerning the following question:

hi, i have a hash like 
%hash=(
   a => 1
   b => 2
}

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How do I 'undef' a hash entry - not the value, but the key? if i write 
undef $hash{a}

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i get 
%hash=(
   a => undef
   b => 2
}

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What i want to get is 
%hash=(
   b => 2
}

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I need this for %ENV modification (UX: unset equivalent).

Replies are listed 'Best First'.
Re: 'undef'ing a hash element
by antirice (Priest) on Aug 26, 2003 at 12:13 UTC

    I believe delete is what you're looking for.

    Hope this helps.

    antirice    
    The first rule of Perl club is - use Perl
    The     ith rule of Perl club is - follow rule i - 1 for i > 1

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      This is exactly what I was looking for. thx
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Re: 'undef'ing a hash element
by arthas (Hermit) on Aug 26, 2003 at 12:17 UTC

    Hi!

    You should use:

    delete $hash{$a}

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    This removes the key/value pair. undef only sets the key's value to the undefined value.

    Michele.

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[d/l]
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      This is a little off-topic, but you may find the info useful in the long run. For fun, check out Hash::NoVivify to learn about a related subtlety of hash key management and a module for dealing with it.
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