Code:

# Print list of word frequencies
{
$0 = tolower($0)
    for (i = 1; i <= NF; i++)
	   
		counter[$i]++	
}

END {
    
    for (word in counter)
        printf "%s\t%d\n",word, counter[word]		
}

I have this simple awk code from awk user guide to count the frequency of word. Now consider the following input to script:
hello HELLO Hello World

The output is:
hello 3
world 1

What if I want it to maintain the case of other words. i.e I want the output as
hello 3
World 1

(Note the case of World is retained). How do I do it. Please help