I don't believe efficiency comes into play, but, your 2nd example "could" be rewritten as 
$foo = defined $bar ? bar : $default_for_foo;

## could be written as, but remember, that 0 is false
$foo = $bar;
$foo ||= $default_for_foo;

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In reply to Re: Effecient shortcut for ?: by PodMaster
in thread Effecient shortcut for ?: by traveler

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