Ok. Let's get back to basics then :)

When you look things up in a hash, you use a string as the index. So your first example is the same as:

$index = 'connection1_size1';
$$hashRecordPtr{$index};
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Do you follow that? The hash index is just any string value.

But what we've done there is to now use a variable as the hash index. Which means that we can now be a bit cleverer.

$index = "connection1_size$count";
$$hashRecordPtr{$index};
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So now we have a double-quoted string, and we've used the value of the variable $count within the string.

So that effectively does what you want, but we can cut out the unnecessary $index variable and use the double-quoted string directly as the hash index.

$$hashRecordPtr{"connection1_size$count"};
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Is that any clearer?

... and of course, there are some times when we need to help the interpreter know when our variable begins and ends. In the example davorg gave you, $count fell at the end of your hash key (index). But suppose you wanted the $count to fall in the middle of your key, like this:

$index = "connection$countsize";
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How would the interpreter know that you were referring to $count? You might have also been referring to $counts, $countsi, $countsiz, or $countsize. In such cases, you would put curly braces around the variable name to delimit it from the rest of the text.

$index = "connection${count}size";
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