Running this code:

use Benchmark qw(cmpthese);
cmpthese(10000000, {
  single => sub {$foo = 'http://www.yoursite.com'},
  double => sub {$foo = "http://www.yoursite.com"},
});
[download]

produces these results on my machine:

            Rate double single
double 2865330/s     --    -2%
single 2915452/s     2%     --
[download]

So it looks like single quotes may be slightly faster, but that may be within the margin of error. I generally use single quotes unless I need interpolation of variables, but it's probably just a matter of preference.

-- Mike

--
just,my${.02}