#! perl -w

$/ = "";  # paragraph mode
while(<DATA>) {
    if(/^dn:/) {  # skip irrelevant paragraphs
    	my($cn) = /^cn:\s*(.*)/m;
    	my($gid) = /^gidNumber:\s*(\d+)/m;
		my(@member) = /^memberUid:\s*(.+)/mg;
        print "cn: $cn\ngid: $gid\nmembers: @member\n\n";
    }
}

__DATA__
*** Your sample data follows ***