I realize pmatch hasn't been written yet, but this seems odd. You're calling (pmatch f pat action) repeatedly, so where is the state info kept regarding the index of the last match, etc.? Your example reminds me of strtok in this regard, but I doubt that's what you had in mind.
With the Ruby example, the scan function invokes the supplied block repeatedly, but the break statement within the block will exit the scan function which is the desired behavior.
It's somewhat moot until someone writes pmatch though.