for my $rc (@R) {
  if ($rc->[0] eq "a") {
    splice @$rc, 0, 2;
  }
}

##</code><code>##

for my $rc (@R) {
  if ($rc->[0] eq "a") {
    delete $rc->[0-2];
  }
}

##</code><code>##

foreach (@records) {
              $buf .= "$_->[0] $_->[1] $_->[2] $_->[3]\n";
              print $buf;
}