So, a lot of people like to say that. And indeed, sometimes index is ten times faster. But sometimes it's more than three times slower!
use Benchmark qw(:all);
$text = <<EOF;
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+aaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+aaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+aaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+aaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+aaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+aaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+aaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+aaaaaaaaaa
EOF
$pattern = "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb";
cmpthese($count, {
'regex' => sub { $text =~ $pattern },
'index' => sub { index $text, $pattern },
});
__DATA__
Rate index regex
index 630601/s -- -67%
regex 1914815/s 204% --
Moreover, increasing the lengths of the text and pattern, I can make the regex be 40 times faster*. See Re^8: "advanced" Perl functions and maintainability for reasons why people use regexes instead of index. Personally, I still don't understand why there even is a difference in speed -- shouldn't the regex engine be optimized to notice that this is a search for a constant string and then call the same function as index?
*: No, I'm not kidding. The output follows. Moreover, for this example, adding a single study $text is an extra 10 times faster, completely obliterating index.
Rate index regex study
index 178/s -- -98% -100%
regex 7538/s 4124% -- -92%
study 98871/s 55311% 1212% --
Update: I'm running perl v5.8.5 built for i686-linux.