If you've got the /s switch on though this'll happily match R\n\n\n, won't it?

Update: Oops, did wrong number of \n's. R\n\n does seem to pass this match, unless the code below is wrong..

#!/usr/bin/perl -w

use strict;

my @tests = (
  "R\n\n",        # Passes
  "Roo",          # Passes
  "roo",          # Fails
  "Roo\n",        # Fails
);

foreach (@tests) {
  if (/^R..\z$/s) {
    print "$_ passes\n";
  } else {
    print "$_ fails\n";
  }
}
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