Here's a benchmark, comparing the difference between a double quoted string, and a single quoted string: 
#!/usr/bin/perl

use strict;
use warnings;

use Benchmark("cmpthese");

cmpthese(-1, {
   "double", q !eval q {$a = "this is a string"}!,
   'single', q !eval q {$b = 'this is a string'}!,
});

[download]
And the results: 
          Rate single double
single 34133/s     --    -1%
double 34462/s     1%     --

[download]
Now, before you think double quotes are faster, the results of another run: 
          Rate double single
double 33810/s     --    -0%
single 33811/s     0%     --

[download]
When I ran this 10 times, double quotes won 5 times, single quotes won 4 times, and there was one tie. The difference was never more than 1%.

So my conclusion, on this single benchmark, is, performance wise, it doesn't matter. If you still want to claim there's a performance difference, come with either a better benchmark, or a discussion of the code of perl that shows there's a difference.

In reply to Re: To Single Quote or to Double Quote: a benchmark by Anonymous Monk
in thread To Single Quote or to Double Quote by NateTut

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