I am confused by the question. Consider

$x = 17;
for $i (1..10){
  $x = sqrt($x);
}
for $i (1..10){
  $x *= $x;
}
print $x;
[download]

prints 17.00000000000002 on my perl 5.005_003 on an x86. Is that an integer? merlin's comment shows how to see if a number is a "good" integer, but if you are using this in some mathematics, you might check for some fudge as it is fairly easy to get a non-integer that "should be" an integer.

You probably knew that, but it might not be obvious to everyone...

--traveler