craigt has asked for the wisdom of the Perl Monks concerning the following question:

I'm working on a Windows platform using an Apache server and dHTML - HTML, CSS, JavaScript, Perl/CGI, and a number of APIs. I have a custom parameter file that's read into a CGI module. The parameters in that file allow a user to customize the geography and appearance of the application. The parameters in that file are embedded in the CSS, JavaScript, and Perl code in the CGI module. I define my Perl namespaces at the beginning of the module, with names like $navytext. I then read the custom parameter file into an array. The parameters in the file have the same names as the namespaces I define in the CGI module. I split the comment portion of each parameter line off and eval the parameter value into the CGI module where it is then used downstream in CSS, JavaScript, and Perl. A simplified code example follows. 

my $navytext; # This variable appears as the line '$navytext = '000066
+' # Navy blue text.' in the custom parameters file below.
.
.
.
my $cpsfnx = $thepdir . 'custom.parms';
if (-e $cpsfnx) {

  my @cpslnsx = in_shared($cpsfnx);

  my $cpsln = '';
  foreach $cpsln (@cpslnsx) {
    if (index($cpsln,'#') > 1) {
      ($cpsln,$tmp) = split ('#',$cpsln);
    }
    eval($cpsln);
  }

}
.
.
.
<HEAD>
<STYLE>
#tabmenu {
          color: #$navytext;
         }

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Notice in the example that the CSS with the Perl namespace $navytext resides right in the Perl module. This has all worked well for some time. Now I would like to remove the CSS from the Perl module, put it in a CSS file, and link the CSS file into the Perl module. When I do this, the Perl variable no longer resolves correctly to the HTML color and the CSS does not work. I have tried to quote the Perl variable in the CSS file in several ways with no luck. The question is can I link an external CSS file with embedded Perl variables into a CGI module so that the Perl variables resolve correctly?

  • Comment on Perl variables embedded in CSS in a CSS file not resolving correctly when the file is linked in
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Re: Perl variables embedded in CSS in a CSS file not resolving correctly when the file is linked in
by Corion (Patriarch) on Oct 05, 2018 at 14:02 UTC

    What you want is to use one of the many templating systems. See Template for a selection of those.

    If you're hell-bent on rolling your own, just to keep the precious Perl variables, my suggestion is to declare them explicitly in a hash and to replace them with a tiny loop:

    my %template_variables = (
    'navytext' => $navytext,
    # ...
);

my $css = <<'CSS';
#tabmenu {
          color: #$navytext;
         }
CSS

sub fill_template {
    my( $str, $vars ) = @_;
    $str =~ s!\$(\w+)!$template{ $1 } || '$' . $1!ge;
    $str
};

print fill_template( $css , \%template_variables );

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[d/l]

      Thanks for the suggestion Corion.

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