Insert lines from one text file to another one 

sed -re ':a;Rfile1' -e 'x;s/^/./;/.{10}/!{x;ba};s/.*//;x' file2

June 22, 2013 — openiduser102

Explanation

This command reads the first line from file2 and then 10 lines from file1, then the second line from file2 and the next 10 lines from file1 and so on.

Limitations

Works in GNU sed.

text-processing file-manipulation
sed

Alternative one-liners

Insert lines from one text file to another one 

awk 'NR % 10 == 1 {getline f2 < "file1"; print f2} 1' file2 | cat -n

June 22, 2013 — openiduser102