To the above answers, I wanted to add this advice: use a subroutine to ask the questions and do the chomping. If you have a subroutine that asks the question, then returns the result, the code will be cleaner. So, summarizing the above advice:

#!/usr/local/bin/perl
 $username = ask_user("What is your name?");
 $userlocation = ask_user("Where do you live?");
 $userage = ask_user("How old are you?");
 $userage2 = $userage++;
 $usersex = ask_user("Are you a boy or a girl?");

 $userboy = get_gender($usersex);

 print "$username is $userage years old and lives in $userlocation"
 ." In a year $userboy will be $userage2 $username is a $usersex";


sub ask_user
{
    my ($question) = @_;

    print "\n$question ";
    my $answer = <STDIN>;
    chomp($answer);

    $answer;
}

sub get_gender
{
    my ($usersex_in) = @_;
    
    my $usersex = lc($usersex_in);

    if ($usersex eq "boy") {
       return "he";
    } 
    elsif ($usersex eq "girl") {
       return "she";
    }
    else {
     return "it";
   }
}
[download]

Hope that was helpful.