RE: Answer: Regex anchor speed ?: Is /^.*X/ faster than /X/ ?

[Dominus]

Ovid said:

> The /^.*\@/ is forced to match to
> the end of the string (or to a newline) and then backtrack to the @ symbol.

But that is not exactly true. In general, Perl does behave that way. But in some cases, such as this one, there is an optimization: Perl sees that the string can't match unless it contains a @ character, so it looks for the @ first, and works outwards from there. In particular, it does not let .* match all the way to the end of the string and then backtrack it; it gets the right length for .* on the first try.

Isn't that interesting?

The nongreedy .*? version is optimized similarly, so I would be surprised if it performed any differently in this example.