Subinstr function not working in STATA 17

[Melat Kassa]

I am looping 10 csv files (which are monthly data) and then trying to generate a month variable as a unique identifier. I tried to use the subinstr function to extract the month value from the file name but the function doesn't work. However, when I type "help subinstr" there is an explanation. Has stata changed the function name? How can I get around the issue. My code is below. X represents 01_2021, 02_2021, and so on all the way to 10_22. I am trying to extract the value "01,02, 03, etc. and make that the month value for the respective csv file.

foreach x of local files {
        di "`x'" // Display file name
        
        *Import each filepath
        qui: import delimited "`x'", delimiter (",") case (lower) clear // Import csv file
        qui : gen id = subinstr ("`x'", "_2021.csv", "", .) // Generate id variable(same as file name but     without _2021.csv)
        
        *Append each file to masterfile
        append using `dataset', force
        save `dataset', replace
        
}

This is the error I get:
subinstr not found
r(111);

[William Lisowski]

Remove the space between the function name subinstr and the left parenthesis following it.

. generate x = sqrt (4)
sqrt not found
r(111);

. generate x=sqrt(4)

.

Added in edit: while spaces are allowed between an option name and its arguments, as your import command demonstrates, they are not allowed between a function name and its arguments, because "sqrt" could be a variable name or a function name, and some way is needed to tell the two apart.

[Melat Kassa]

Thank you, William! I didn't know functions behaved differently when it came to spaces.