See the current Perl documentation for int.
Here is our local, out-dated (pre-5.6) version:
int - get the integer portion of a number
Returns the integer portion of
EXPR is omitted, uses
$_. You should not use this for rounding, because it truncates towards
0, and because machine representations of floating point numbers can
sometimes produce counterintuitive results. Usually sprintf() or printf(), or the
POSIX::ceil functions, would serve you better.