I'll third the AnonyMonk's second, and only add that the integer pragma is lexically scoped, so there's some leeway for creative use of it:

c:\@Work\Perl\monks>perl -wMstrict -le
"my $z = S(2, 7);
 print $z;
 $z += 2.345;
 print $z;
 ;;
 sub S {
   use integer;
   my ($x, $y) = @_;
   return $x * ($y + 1.234);
   }
"
16
18.345
[download]

Oh, and BTW, integer applies to operations, not variables!