http://www.perlmonks.org?node_id=134853


in reply to Supressing zero values in formatted reports

From the perlform manpage:
Picture fields that begin with ^ rather than @ are treated specially. With a # field, the field is blanked out if the value is undefined. For other field types, the caret enables a kind of fill mode.
So change your @#### to ^####, and make sure the values you want to suppress are undefined.

The second problem is that using an undefined value when warnings are enabled will generate several warning messages. I suggest disabling warnings within the format, like this:

{ no warnings; format STDOUT = @<<<<<<<<<<<<< ^#### @#####.## $output[$i], $output[$i+1], $output[$i+2]/1024 . }