As you probably got, with 
delete ($location_hash->{ $city }) ;
delete ($location_hash->{ $city }->{ 'ZIP' } );

[download]

you delete the $city key and immediately create it again with value being the reference to empty hash. In the argument of second delete you treat $location_hash-{$city} as hash reference and Perl is "clever enough" to create it for you. So you end up with new ($city => {}) pair in %{%location_hash}.

I personally dislike this automatic structures creation (it affects arrays also) and believe that decent and clearly read operation should not modify your data but raise an exception instead because you are treating undefined value as hash reference.

Nevertheless, it can be useful for you to know, that delete returns the value deleted 

my $city_ref = delete ($location_hash->{$city});
delete($city_ref->{'ZIP'});

[download]

In reply to Re: How can I delete a key' value from a hash by roman
in thread How can I delete a key' value from a hash by kevyt

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.