in reply to Clear / Initialize multiple hashes

Not exactly. By using my, you declare new hashes. If you used warnings, Perl would tell you: 
"my" variable %hash1 masks earlier declaration in same scope

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So, the statement is equivalent to 

my (%hash1, %hash2, %hash3);

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Note that the hash %_ is not cleared, because the body of the loop is not run (the brand new hashes are emtpy).

Without my, %_ would be cleared, but %hash1 and company would stay untouched. To test, just play with comments in the following code: 

# use strict;
use warnings;
%_     = (u => 2);
%hash1 = (b => 3);
# %hash1 = (b => 3);
# %_ = () for my (%hash1,%hash2,%hash3);
# %_ = () for (%hash1,%hash2,%hash3);
print %_, %hash1, "\n";

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To clear a hash, use undef or %hash = ().

لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

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Re^2: Clear / Initialize multiple hashes
by acadey (Initiate) on Sep 19, 2013 at 18:19 UTC

    Thanks! both replies helped a lot. I thought it looked a little funky and thought I would check so I am really glad I did. Any suggestion on the best way to clear all of them? At initialization I can just do:

    my(%hash1,%hash2,%hash3);

    but later on if I want to clear all of them how should I go about it? I mean I could just clear each one individually, but when I have a long list that can be a bit of a pain...

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[d/l]
      but later on if I want to clear all of them how should I go about it?

      The simplest way is to scope them such that they get reinitialised by re-entering the scope each time you want to re-use them:

      for( some loop condition or contruct ) {
    my( %hash1, %hash2, %hash3 );
    ## do stuff with them ...
}

      [download]

      Each time that loop iterates, the hashes will be reinitialised for you.

      But, it you really need to do it manually, you could use:

      undef %$_ for \(%h1,%h2,%h3);

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      With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
      Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
      "Science is about questioning the status quo. Questioning authority".
      In the absence of evidence, opinion is indistinguishable from prejudice.
[reply]
[d/l]
[select]
      You can do
      ( %hash1, %hash2,  %hash3 ) = ();
# or
%hash1 =  %hash2 = %hash3   = ();

      [download]
      لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ
[reply]
[d/l]

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