Error, missing operation after conditional break - break

Question

I am trying to run this procedure, but am getting an "Error, missing operation", highlighting the conditional break:
is_prime := proc()
    local i, x_check;
    printf(`Enter an integer to check if it is a prime number...`);
    x_check:=parse(readline(terminal));
    if x_check<=2 then
        printf(cat(x_check,` is a prime number.`));
    else
        for i from 2 to x_check-1 do
              if (irem(x_check,i)=0) then
                 printf(cat(x_check,` is not a prime number.`));
                 break 2;
            end if;
          end do;
        printf(cat(x_check,` is a prime number.`));
     end if;
end proc:
If I don't include the integer, I am able to run the procedure, but it does not function like I would like it to. I am running Maple 2022, and can successfully run the example conditional break code in the Help. What is wrong with my use of break?
I am unfamiliar with conditional break, so beyond removing the integer, I do not know what else to try. I wanted to exit out of the outer if statement, and thought break would be able to do this so that my last printf statement is not displayed.

Answer 1

The break functionality is for do-loops, not if-then.
So your expectation of its breaking out of the your outer if-then is not reasonable.
The reason that you're getting an error message is that you attempted break 2 within only a single level (ie. unnested) do-loop. So it's invalid to instruct it there to break out of two levels of looping.
Since there's nothing else that you don't want to happen at the stage in question, you could get by with just return at that juncture.
It's not best practice to use name-quotes (single left-ticks) inside printf, for the English text. Those are just names, and in the worst scenario might even have been assigned some value. (Unlikely, but let's be careful.) Instead, the printf command offers its own neat syntax for formatting its message, using safe strings. Let's do that below.
And, for fun, I changed your readline to a readstat, to get a more meaningful title in the popup query.
is_prime := proc()
local i, x_check;
x_check:=readstat("Enter an integer to test its primality");
if not type(x_check,posint) then return
elif x_check<=2 then
printf("%a is a prime number.\n",x_check);
else
for i from 2 to x_check-1 do
if (irem(x_check,i)=0) then
printf("%a is not a prime number.\n",x_check);
return;
end if;
end do;
printf("%a is a prime number.\n",x_check);
end if;
end proc:
is_prime();
ps. Do you want to handle the input 1 differently?