Cannot modify global variable in function in PineScript

This is my Pinescript code.

//@version=5
indicator("Strategy", overlay=false)

var count = 0
count := nz(count[1],0)

counter() =>
    count := close > close[1] ? count + 1 : count

counter()

plot(count)

Here I am facing an issue in my counter function. I am getting an error in the count inside my counter function. Cannot modify global variable 'count' in function; error displaying in Pinescript compiler. I tried with Var also. still facing the same issue. Please help me to resolve this.

The count variable should be defined inside of the function. Also, the count variable will not be available outside of the function.

The following will work:

//@version=5
indicator("Strategy", overlay=false)

counter() =>
    var count = 0
    count := nz(count[1],0)
    count := close > close[1] ? count + 1 : count
    count

new_count = counter()

plot(new_count)