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>
[download]

#!/usr/bin/perl
use strict;
use warnings;
use CGI;

my $cgi = CGI->new;

my $question= $cgi->param("question");
my $answer = $cgi->param("answer");
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