awk -v want="RECORD_COUNT,VALUE2,VALUE3" -F'[=\\][]' '  --- F'[=\\][]' need to understand how the regular exp works.. 
function prnsection(i) {                                --- function pass arg i in
   if(length(section)) {                                --- if section is not empty do following
     printf "%s",section;                               --- print section
     for(i=1;i in keypos;i++) {                         --- for loop, max i is number of array keypos: keypos[value1]=1, keypos[value2]=2, keypos[values3]=3 
       printf " %s", keys[keypos[i]]                    --- array keys elements are: keys[1]=value1, keys[2]=value2, key[3]=value2 
       keys[keypos[i]]="MISSING"                        --- if array keys element doens't have value , assign value "missing"
     }                                                 
     printf "\n"
   }
}
BEGIN {
   for(i=split(want, keypos, ",");i;i--) {              --- create array keypos element based on variable want
       keys[keypos[i]]="MISSING";                       --- create array keys if keys is empty then assign value missing.
   }
}
NF>2 { prnsection(); section=$0 }                       ---if NF> 2  then call function and assign $0 to section. the function has one 
                                                                                    --- argument, but here is empty, 
														---how the value be passed in?	
														---what's the purpose to call this function?
$1 in keys { keys[$1]=$0 };                             --- first my understanding is $1 is VALUE1, VALUE2..., I tried command, with -F'[=\\][]' 
                                                                           ----as delimiter, NF=1, not sure how it works. 
END { prnsection() }' file                              ---here call the function to print result..