I copied your code and data verbatim and it works for me.

howard$: cat input.txt
77      *       10      0       *       *       0       340
141     *       40      0       *       *       0       240
howard$: perl -lane 'print "$F[2]\t$F[7]" if $F[7] > 0' < input.txt
10      340
40      240
[download]

Environment is AIX, Perl 5.8.8.