my %stats;
while (<FILE>) {
    next unless /^(jack_average)\w+:\s+(\d+\.\d+)$/;
    $stats{$1}{count}++;
    $stats{$1}{sum} += $2;
}

printf( "%20s %5s %8s\n", "Name", "Count", "Average" );
for ( sort keys %stats ) {
    printf( "%19s: %5d %8.2f\n", $_, $stats{$_}{count},
             $stats{$_}{sum} / $stats{$_}{count} );
}