Since it is OK for you to run it online I strongly recommend to make a Google Sheet for this task so you can access it from everywhere and also to manipulate easily CSV records (import - export) as you mentioned.
This is how I created it (at the end there is a link for it but I will also give instructions in case the link is not working for others at future):
1. Create a Google Sheet
2. Use the first column (let's say A) to enter your multiple numbers or paste them massively from your CSV.
3. The second column (let's say B) will be used to calculate the percentage differences for each value from the left
In this part you have to input the following calculating formula to all column cells. You can paste it in all cells at once by selecting the Column Letter holding the cmd or ctrl button and then paste by holding cmd+enter or ctrl+enter.
- note the XX value for the next step, so is better to already know which cell you are going to use on Step 4
- (-100) at begining is important so it gives you positive percentage numbers when the values are bigger from the base value.
4. Finally on another cell (let's say 2nd cell from E column) use it as an input for base number on which you want to calculate the percentage difference for each number you input
Now let's say that for this step you use the cell E2. You will replace the XX with that cell, like
You will have the following result (I reformatted it for visually improvement)
I published it here so you can examine it or download and start using it.
PS If you need to find how much "far" or "close" is the percentage of the input number to the base number, you can add +100 at the end of the formula.