I think most of the answer to this question is HTML not Perl, but I'll answer it anyway.
The easy way of selecting a question would be an HTML select list.
<form method="post" action="http://myserver/perl_script">
<p>Which question do you want to answer?
<select name="question">
<option value="1">Question 1</option>
<option value="2">Question 2</option>
<option value="3">Question 3</option>
<option value="4">Question 4</option>
</select>
</p>
<p>Answer your question in the textbox:<br />
<textarea name="answer" rows="20" cols="70"></textarea>
<input type="submit" value="submit"/>
</form>
The Perl script to read the answers would be something like
#!/usr/bin/perl
use strict;
use warnings;
use CGI;
my $cgi = CGI->new;
my $question= $cgi->param("question");
my $answer = $cgi->param("answer");
If you spot any bugs in my solutions, it's because I've deliberately left them in as an exercise for the reader! :-)