in reply to Merging files, 1 line for every 10

A one-liner:

perl -ple"printf q[%s], scalar <STDIN> unless $n++ % 10" file1 < file2

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.