Ideally, you'd give checkboxes different names:
(Using a travel agent site as an example.)

# <input type="checkbox" name="search_first_class">
# <input type="checkbox" name="search_economy_class">

my $search_first_class   = $cgi->param('search_first_class');
my $search_economy_class = $cgi->param('search_economy_class');

warn("Classes to search:"
   . ($search_first_class   ? ' First'   : '')
   . ($search_economy_class ? ' Economy' : '')
) if $DEBUG;
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But you can give them the same name if they have different values:

# <input type="checkbox" name="search_class" value="first">
# <input type="checkbox" name="search_class" value="economy">

# Call $cgi->param in a list context.
my @search_classes = $cgi->param('search_class');

warn("Classes to search: " . join(' ', @search_classes))
   if $DEBUG;

# # The array can be converted to a hash for easy to lookup.
# my %search_classes;
# @search_classes{@search_classes} = @search_classes;
#
# warn("Classes to search:"
#    . ($search_class{'first'  } ? ' First'   : '')
#    . ($search_class{'economy'} ? ' Economy' : '')
# ) if $DEBUG;
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Update: I concur with Ovid. The second case is the ideal one, not the first. What was I thinking??

You have the order reversed. Ideally, you should give each input the same name with a different value. The reason for that is one of maintainability. If you have different names, you generally have to write code to handle each name. However, in a well-designed app, if the only a new value is added, you may not have to change the code:

  Football: <input name="sport" value="football" type="checkbox" /><br
+ />
  Baseball: <input name="sport" value="baseball" type="checkbox" /><br
+ />
  Soccer:   <input name="sport" value="soccer"   type="checkbox" /><br
+ />
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With those three inputs, you can often use just one basic line to handle them:

  foreach my $sport ($cgi->param('sport') {
    # do something with sport
  }
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If handled correctly, adding a new sport is now just adding a new input box. By using different names, I'd like have to write a new input box and write new code.

Cheers,
Ovid

New address of my CGI Course.

thanks for all those suggestions, proved to be very useful

Each checkbox group⁰ should have its own name. Your assignment should fetch the value of the checkbox named 'option1'. Your HTML might look like this:

<form action='submission.pl' method='post'>
  <input type='checkbox' name='option1' value='Option 1 checked!' />
  This is the text next to option 1
  <input type='submit' value='Submit' />
</form>
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Adding more checkboxes with the same name will result in different or multiple values. If you use CGI::Simple (which I recommend as a CGI drop-in replacement), the multiple values will returned as an array. So, your Perl code might contain something like:

my @value = $cgi->param('option1');
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0: Updated 09.Jun.2005 @ 14:40 CST. Re-read revealed an oops.

@values = $query->param('foo')
That will get all of the values checked.

As stated below check out the CGI.pm docs.