Perlbuzz news roundup for 2014-09-15

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These links are collected from the Perlbuzz Twitter feed. If you have suggestions for news bits, please mail me at andy@perlbuzz.com.

Template Toolkit's DEFAULT does not do short-circuit evaluation like you might think it would.

If you have

[% DEFAULT foo = user.calculate_foo; %]

Then the results of the method call user.calculate_foo are assigned to foo, unless foo already has a true value.

However, whether or not foo already has a true value, user.calculcate_foo is always invoked.

You might expect the code to look like this:

$foo = $user->calculate_foo() unless $foo;

But it's really like this;

$temp = $user->calculate_foo();
$foo = $temp unless $foo;

So, if user.calculate_foo is an expensive function that you don't want to invoke unless you have to, you'll have to resort to an explicit IF block:

IF !foo;
    foo = user.calculate_foo;
END

It's also worth noting that DEFAULT is not for checking if a variable is set, but for checking if it is true.

These links are collected from the Perlbuzz Twitter feed. If you have suggestions for news bits, please mail me at andy@perlbuzz.com.

These links are collected from the Perlbuzz Twitter feed. If you have suggestions for news bits, please mail me at andy@perlbuzz.com.

These links are collected from the Perlbuzz Twitter feed. If you have suggestions for news bits, please mail me at andy@perlbuzz.com.

These links are collected from the Perlbuzz Twitter feed. If you have suggestions for news bits, please mail me at andy@perlbuzz.com.

These links are collected from the Perlbuzz Twitter feed. If you have suggestions for news bits, please mail me at andy@perlbuzz.com.

These links are collected from the Perlbuzz Twitter feed. If you have suggestions for news bits, please mail me at andy@perlbuzz.com.

These links are collected from the Perlbuzz Twitter feed. If you have suggestions for news bits, please mail me at andy@perlbuzz.com.

These links are collected from the Perlbuzz Twitter feed. If you have suggestions for news bits, please mail me at andy@perlbuzz.com.

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