}
# Compile mode flags.
if ($Arg =~ /^-[D,I,U,isystem](.*)$/) {
if ($Arg =~ /^-(D|I|U|isystem)(.*)$/) {
my $Tmp = $Arg;
if ($1 eq '') {
if ($2 eq '') {
# FIXME: Check if we are going off the end.
++$i;
$Tmp = $Arg . $ARGV[$i];
