foreach (5.6, 2, 5.000000001, 3, -2, -3, -4.12){
   print &is_int ($_)?"$_ is an integer\n":"$_ is not an integer\n";
}

sub is_int{
    my $testvar =shift;
    use integer;
    my $intval=$testvar_*1;
    no integer;
    return $testvar == $intval;
}