Review a filter diceroller

Hi.
I'm not a PHP programer or a drupal hacker or regexp fan.
Based in the other filters I create a diceroller filter and want a code review of this.
The input string is xdy where x is the number of dices and y is the number f sizes of dice.
or.. x is the number of runs of rand function and y the range of the rand function. the output is "[ rand result ] [rand result]... one for each dice.

I copied pro the folder modules/tribune/filters and it not work.
Can you yell-me what is the problem?

Note:
The extension is .txt only because the upload filter. The real is .inc like other filters.