use strict;

use CGI;
use Template;

$|++;


# Dispatch table is a hash where
# every value is a sub-reference
# When the user doesn't provide
# a run-mode, then list() is
# triggered (default case, see
# the last line

my %dispatch_table = (
        list => \&list,
        item => \&item,
        fetch_image => \&fetch_image,
        '' => \&list,
);

my $query = new CGI;

print $query->header;
print $query->start_html(
  -title => 'A small example...'
);

# Now we read the param mode from
# the query. The string is used to
# fetch the hash table. We got a
# reference to a function, so we
# can call it...

my $mode = $query->param('mode');
&{ $dispatch_table{$mode}};

print $query->end_html;

sub list
{
    print "<h1>List mode</h1>\n";

    my $action = $query->param('action');

    # What we can do with $action?
    # Another dispatch table here is not
    # possible (one can't define procedures
    # local to other procedures, like in 
    # Pascal). Another possibility is to 
    # define other procedures "at the same
    # level" of list(), item() and so on...
    # but it isn't elegant and easily maintanable.
    # So we could use different
    # packages for different "top level run-modes".
    # Or, simply, we can cope with $action
    # here, with a if-elsif-else construct.

}

sub item
{
    print "<h1>Item mode</h1>\n";
}

sub fetch_image
{
    print "<h1>Fetch_image mode</h1>\n";
}