Notice the use of the scalar operator:

for($i = 0; $i <  scalar @bestpix; $i++) 
{
  print "$bestpix[$i]\n" 
}

The value of an array in scalar context is the number of elements in the array. So the value of scalar @bestpix is the number of elements in the @bestpix array.
In Perl, the type of an expression is often taken from the context, rather than a fixed set of rules. In cases where the context may be ambiguous, or give you a type that you don't expect, you can use the scalar operator to force an expression to a scalar context.

print <STDIN>;

will print all the lines from the standard input (usually the keyboard) and then finish. But what if you only want to print one line? You could use an intermediate variable like this:

$line = <STDIN>;
print $line;

print scalar <STDIN>;