You need to add inputs and a submit button in hello.pl

# hello.pl
use CGI;
use strict;
my $cgi = CGI->new();
my $fname = $cgi->param('firstname');
my $lname = $cgi->param('lastname');

print "Content-Type: text/html\n\n";
print $cgi->start_html;
print <<HTML;
<h3>Hello</h3>
<table cellpadding="5">
<tr>
 <td>Firstname</td>
 <td><b>$fname</b></td>
</tr>
<tr>
 <td>Lastname</td>
 <td><b>$lname</b></td>
</tr>
</table>

<form method="post" action="welcome.pl">
<input type="hidden" name="firstname" value="$fname"/>
<input type="hidden" name="lastname" value="$lname"/>
<input type="submit"/>
</form>

</body>
</html>
HTML
[download]

and amend welcome.pl

#!perl
# welcome.pl
use CGI;
use strict;
my $cgi = CGI->new();
my $x = $cgi->param('firstname');
my $q = $cgi->param('lastname');

print "Content-Type: text/html\n\n";
print $cgi->start_html;
print <<HTML;
<h3>Welcome</h3>
<table cellpadding="5">
<tr>
  <td>Firstname</td>
  <td><b>$x</b></td>
</tr>
<tr>
  <td>Lastname</td>
  <td><b>$q</b></td>
</tr>
</table>
</body>
</html>
HTML
[download]