For example, we have a string:
s = "321"
To check if the last symbol is "1", we might just try to remove (or replace with an empty string) the symbol "1". If the string changed, then there was the symbol "1" in the string:
s2 = str .replace_all (s, "1", "")
now s2 is "32", so
s == s2 returns false.
But we can't find out what the position of the symbol "1" was and if there was only one symbol "1".
To be sure, we just add a special character (I use ';') to the end of the string, and then try to remove not just "1", but the string "1;":
s = "321;"
s2 = str .replace_all (s, "1;", "")
Now, if s != s2, then we might be sure, that last symbol of the string was "1". And then we might check for all digits and get information about what digit we have and at what position. Same for additional symbols: decimal point and minus.
In true TradingView spirit, the author of this script has published it open-source, so traders can understand and verify it. Cheers to the author! You may use it for free, but reuse of this code in a publication is governed by House Rules. You can favorite it to use it on a chart.