use ExtUtils::MakeMaker qw' prompt ';
...
if( prompt('Are you new?', 'n') =~ /y/ ){
   my $username = prompt('Your name is?','John Smith');
   $username =~ s/\s+$//;
   ...
} else {
   my $username = prompt('Who are you','John Smith');
   $username =~ s/\s+$//;
   ...
}


##</code><code>##

if( prompt('Are you new?', 'n') =~ /y/ ){
   CreateNewUser();
} else {
   ActivateOldUser();
}