Actually no.

Double quotes are optimised away by the compiler. In the case of no variables actually being interpolated, then double quotes work exactly the same way single quotes do. Effectively all the compiler does when it sees a variable in double quotes is turn something like:

"Error $@ in $file"
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into:

"Error " . $@ . " in " . $file;
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I know Doug MacEachern was also talking about optimising things so that in some cases you might optimise it into a join, or simply a comma separated list of strings and variables. But I don't think he's submitted any patches to do that just yet.