perl -le 'my @a = <>; chomp @a; print join ",", @a' file

BTW, That's a useless use of cat.

Update: Here's an alternative to avoid reading the whole file into memory: 

perl -e '{ $_=<>; chomp; print; last if eof(); print ","; redo }; prin
+t $/'

[download]

-sauoq
"My two cents aren't worth a dime.";

In reply to Re: perl 1-liner to join a list? by sauoq
in thread perl 1-liner to join a list? by bfdi533

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