Something

filelength=wc -l array.txtfor ((i=1;i<=filelength;i+=1)) do if [ sed -n $i/<key>.*<\/key>/p array.txt ]for ((j=i;j<=filelength;j+=1)); doif [ sed -n $i /<string>.*<\/string>/p array.txt ] then# insert code that will take key and string and insert them into an arrayfidonefidone