my $first=0;

while (<DATA>) {
	chomp ($_);
	my $element = $_;
	if ($first == 0) { 
		$first = 1;   # don't print a comma before the first element
	} else {
		 print ",";    # print a comma
	}
     print $element;
}

print "\n";

__DATA__
foo
bar
blivitz
this is a line
1
2
a
b
cde

##</code><code>##

foo
,bar
,blivitz
,this is a line
,1
,2
,a
,b
,cde