perlre describes 2 experimental code features that can do this. Albeit in an ugly way:

@x = split /(?{
    # This populates $^R
    pos()
  })some pattern(??{
    # This returns an impossible pattern for long matches
   (pos()-$^R < 5) ? "" : "no\\bmatch"
  })/, $string;
[download]

Be warned though that this will backtrack and try to match again. For instance if you want to not match more than 4 ,'s, this will match 4 out of 6 commas, then will match 2 commas next time. So instead of preserving 6 commas you'll eat them up and get a blank field.

If this is not what you want then you have to do a lot more work. You have to make sure that it fails on all of the backtracks as well. This means that when you fail you need to remember the failure and fail every time you see that position. Like this:

# Be sure that these start clean!
my %bad_r;
my %bad_pos;
@x = split /(?{
    # This populates $^R
    pos()
  })some pattern(??{
    # This returns an impossible pattern for long matches
    if (pos()-$^R < 3
      and not $bad_r{$^R}
      and not $bad_pos{pos()}
    ) {
      "";
    }
    else {
      $bad_r{$^R}++;
      $bad_pos{ pos() }++;
      "no\\bmatch"
    }
  })/, $string;
[download]

That is ugly! But it should work.

Update: Well it should if I had not missed the closing paren on the pos(). Thanks to ikegami for catching that.

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