First, change your @pages array to a hash. Then you can step through this with a:

foreach $page (keys %pages) {
}
[download]

rather than the cumbersome and obfuscated for(){} loop above.

Second, a lot of your regexes don't need the /s modifier. See perldoc perlre for info about that.

Third, use strict.

And now for code error issues: I don't see where you set $keeperlength before using it in your nested for(){} loop. Incidentally, your changing of <tag> to {{{tag}}} doesn't account for things like <br />. That's a minor nitpick, though. Other than that, I can't see why it would "revert" back to the original $html variable. Wanna fix these things I've pointed out (or point out my flaws in thinking as the case may be =]) and try it, and if it still doesn't work point us to some pages that do and pages that don't work and we'll continue hammering.

Good luck!

-marius