.
.
.
my %defines;
while(<FILE>) {
    chomp;
    if (/^#DEFINE \s+ <(\w+)> \s+ (.*) $/x) {
        my ($def, $text) = ($1, $2);
        1 while $text =~ s/<(\w+)>/$defines{$1}/;
        $defines{$def} = $text;
    }
}
.
.
.