Re: How do I make all the values in %a with common keys in %b equal to %b's keys?

Iterate through each key in %a. If %b contains the current hash key, set %a's value to %b's value for that key.

foreach(keys %a){
  $a{$_} = $b{$_} if exists $b{$_};
}
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Editor's note:
Or, as merlyn has pointed out, hash slices can make you very happy...

@a{keys %b} = values %b;
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(dkubb) Re: (2) Answer: How do I make all the values in %a with common keys in %b equal to %b's keys? by dkubb (Deacon) on Mar 30, 2001 at 13:22 UTC
The second answer may be incorrect. According to the question: we are to find all the matches between the keys in `%a` and `%b`, and if there is a match, assign the value of the matching element from `%b` into the corresponding element in `%a`. A hash slice won't work in this case, consider: `my %a = ( a => 1, b => 2, c => 3, ); my %b = ( b => 4, d => 8, f => 12, ); @a{ keys %b } = values %b;` [download] Now, `%a` is: `%a = ( a => 1, b => 4, c => 3, d => 8, f => 12, );` [download] Which is the incorrect answer, according to the question. If we use a hash slice, we'll be copying all the elements from `%b` into `%a`, regardless if there are any matches, or not.	[reply] [d/l] [select]

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(dkubb) Re: (2) Answer: How do I make all the values in %a with common keys in %b equal to %b's keys?
by dkubb (Deacon) on Mar 30, 2001 at 13:22 UTC

The second answer may be incorrect. According to the question: we are to find all the matches between the keys in %a and %b, and if there is a match, assign the value of the matching element from %b into the corresponding element in %a.

A hash slice won't work in this case, consider:

my %a = (
  a => 1,
  b => 2,
  c => 3,
);

my %b = (
  b => 4,
  d => 8,
  f => 12,
);

@a{ keys %b } = values %b;
[download]

Now, %a is:

%a = (
  a => 1,
  b => 4,
  c => 3,  
  d => 8,
  f => 12,
);
[download]

Which is the incorrect answer, according to the question. If we use a hash slice, we'll be copying all the elements from %b into %a, regardless if there are any matches, or not.

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