use Benchmark qw(cmpthese);

my $str= "This is a test, " x 200;
my $single= "'".$str."'";
my $double= '"'.$str.'"';
cmpthese( -3, {
    a_double => sub { eval $double },
    b_single => sub { eval $single },
    c_double => sub { eval $double },
    d_single => sub { eval $single },
} );