use XML::Simple qw(:strict XMLout);  
my $java_opts_X = '-Xmx2g -Xms2g -XX:PermSize=256M -XX:MaxPermSize=256M -XX:NewSize=512M -XX:MaxNewSize=512M';  
print XMLout { java => [ { java_opts => [ grep $_, split qr/[- ]/, $java_opts_X ] } ] },  
    KeyAttr => undef, RootName => 'data';  
  
__END__  
<data>  
  <java>  
    <java_opts>Xmx2g</java_opts>  
    <java_opts>Xms2g</java_opts>  
    <java_opts>XX:PermSize=256M</java_opts>  
    <java_opts>XX:MaxPermSize=256M</java_opts>  
    <java_opts>XX:NewSize=512M</java_opts>  
    <java_opts>XX:MaxNewSize=512M</java_opts>  
  </java>  
</data>