note sundialsvc4 One of the trickiest notions in Perl is the issue of contexts.   When you wrote <tt>$sum += @_</tt>, you used an @array value in a $scalar context.   That changes what it does. For debugging such things, I would insert a statement within the loop that prints useful information to the STDERR file, e.g.:   <tt>print STDERR "sum is $sum\n";</tt>. All interactive programs have two output streams, <tt>STDOUT</tt> and <tt>STDERR</tt>, the latter intended for error or diagnostic outputs. Also, get used to now putting these two statements at the start of every program: <tt>  use strict;   use warnings;</tt> 999655 999655