autark has pointed out that Perl is quite capable of optimising the strings and using the correct quotes, but I always make sure that I only use double quotes when something is being interpolated within the string for another reason.

I think that using the "correct" quotes is a useful code documentation tool. When people come along and maintain my code, the presence of double-quotes around a string should signal to them "look, there's something interesting going on in this string".

But it probably just comes down to personal preference.

--
<http://www.dave.org.uk>

"Perl makes the fun jobs fun
and the boring jobs bearable" - me