LINE:
while ( my $line = <> )
{
    my $n_305_1 = 0;
    my $n_in_range = 0;
    foreach my $chunk ( split /,\s*/, $line )
    {
        # skip non-numeric
        next unless $chunk =~ /^[\d.+-]+$/;

        # skip values outside the range
        next unless 296.1 <= $chunk && $chunk <= 314.0;

        # only allowed one value in the given range...
        if ( ++ $n_in_range >= 2 )
        {
            print $line;
            next LINE;
        }

        # and we can only ignore one 305.1
        if ( approx_equal( $chunk, 305.1 ) &&
             ++$n_305_1 > 1 )
        {
            print $line;
            next LINE;
        }
    }

    print $line unless $n_in_range == 1 && $n_305_1 == 1;

    if ( $n_in_range == 0)
    {
        warn "ill-formed line $.: no values in range";
    }
}