Perhaps I'm missing something, but the original request didn't say anything about doing recursive processing. Assuming that it's required, based on the OP's use of 'File::Find' in his script (which he's not actually using) may not be appropriate.

Perl-only solution from the command line (processes all files in the current directory, ignores lines that don't have commas, converts the file content to a single line of CSV):

perl -i -0wpe's/\A[^\n]+\n//;s/\n(?!\Z)/,/g' *
[download]

-- 
Human history becomes more and more a race between education and catastrophe. -- HG Wells