How do I fix my release mouse on key press script?

I'm trying to make a script that allows the player to release their mouse when they press "R", but it's not working. I'm using an IntValue (parented to the script) as a detection mechanism (if the value is 0, then it's false. If the value is 1, it's true,) I don't need anybody to rewrite the script, I just need to know what to change about it.

local Player = game.Players.LocalPlayer
local UIS = game:GetService("UserInputService")
local PlayerGUI = Player:WaitForChild("PlayerGui")
local IsReleasing = script.IsReleasing.Value
UIS.InputBegan:Connect(function(Input)
	if Input.KeyCode == Enum.KeyCode.R and IsReleasing == 1 then 
		IsReleasing = 0	
		local GUI = Instance.new("TextButton")
		if GUI.Modal == false then
		GUI.Parent = PlayerGUI.ScreenGui
		GUI.Transparency = 1
		GUI.Modal = true
		elseif IsReleasing == 0 then
			GUI.Modal = false
			print("Worked")
		IsReleasing = 1
        end
	end	
end)

This script is parented to StarterPlayerScripts.

EDIT:

local Player = game.Players.LocalPlayer
local UIS = game:GetService("UserInputService")
local PlayerGUI = Player:WaitForChild("PlayerGui")
UIS.InputBegan:Connect(function(Input)
local IsReleasing = script.IsReleasing
if Input.KeyCode == Enum.KeyCode.R and IsReleasing.Value == 1 then
IsReleasing.Value = 0
local GUI = Instance.new("TextButton")
if GUI.Modal == false then
GUI.Parent = PlayerGUI.ScreenGui
GUI.Transparency = 1
GUI.Modal = true
elseif IsReleasing.Value == 0 then
GUI.Modal = false
print("Worked")
IsReleasing.Value = 1
end
end
end)

Your IsReleasing variable is becoming invariable as you're only setting it once. The variable is being set from when the script loads. Since you're not setting it after it has loaded, it will remain the same value from that point.

Move the variable inside the InputBegan event, so it updates with each key press.

EDIT in regards to your response:

It isn't updating the IntValue because you're not changing the IntValue's value. All you're doing is just hard storing the intvalue's value to the variable and then changing the variable instead of the intvalue's value.

local variable = IntValue.Value -- Setting the variable to the value of the IntValue

variable = 1 -- is just changing the variable to "1", not changing the value of the intvalue.

In the code above, on the first line, what's happening is that the intvalue's value is being hard stored to the variable. Whenever you change the variable it's just going to change the variable instead of changing the IntValue's value.

To have it change the IntValue's value you need to store the actual object to the variable and call .Value on it.

local variable = IntValue -- Is now referring to the IntValue object

variable.Value = 1 -- is now changing the value of the IntValue to 1

Hmm... this doesn't seem to be working. I've located the main problem though: the IntValue isn't even updating.