Hi, This is what I've found in CGI documentation

"
...
If a value is not given in the query string, as in the queries ``name1=&name2='' or ``name1&name2'', it will be returned as an empty string. This feature is new in 2.63.
...
"

So, as you don't give any value to the param 'comment'

$comment = param('comment');
[download]

$comment will have the empty value ''.
Then
unless ($comment) { $comment = 'No comment'; }
will update $comment to 'No comment' (An empty value is false, so $comment evaluates to false, an the code is executed)

I'm using version 2.36 1997/5/10 8:22 and I can't see any difference in behaviour. I get the same result.

Regards

Hopes