Just a style suggestion. Using whitespace doesn't slow Perl down, but speeds up reading a script, because it makes things more clear.

You now have:

    # Variables:
    my $pagetitle; # page's title
    my $author; # author's name
    my $copyright_holder; # the copyright holder
    my $chartset; # character set
    # Does $chartset have to be the same as
    # $encoding in page_specs?
    my $default_keywords;
    my $default_description;

    # Variable defaults:
    $pagetitle="PUT-YOUR-TITLE-HERE";
    $author="mynamehere";
    $copyright_holder=$author;
    $chartset="iso-8859-1";
    $default_keywords="";
    $default_description="";
[download]

While I think the following is clearer:

    # Variables:
    my $pagetitle;                    # page's title
    my $author;                       # author's name
    my $copyright_holder;             # the copyright holder
    my $chartset;                     # character set
                                      # Does $chartset have to be the
                                      # same as $encoding in page_spec
+s?
    my $default_keywords;
    my $default_description;

    # Variable defaults:
    $pagetitle           = "PUT-YOUR-TITLE-HERE";
    $author              = "mynamehere";
    $copyright_holder    = $author;
    $chartset            = "iso-8859-1";
    $default_keywords    = "";
    $default_description = "";
[download]

You first use my, and then assign. You can have an assignment directly after my:

    my $pagetitle        = "PUT-YOUR-TITLE-HERE";
[download]

Making the names shorter and using a hash can also help a lot:

    my %hash = (
        title       => 'PUT-YOUR-TITLE-HERE',
        author      => 'mynamehere',
        copyright   => 'mynamehere',
        charset     => 'iso-8859-1',
        keywords    => '',
        description => ''
    )
    # hash values can be accessed as $hash{title} etc.
[download]

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