Perl for Web Site Management

Building a Form

Now let’s turn our attention to the &show_student_form routine. When this routine runs, it produces an HTML page that looks something like Figure 17-1.

Figure 17-1. Form produced by the make_page.cgi script

Examining the subroutine code in more detail, we see that after some preliminaries it has the following:

    $content = join "\n",
        "<P ALIGN=\"center\"><STRONG><A HREF=\"$web_root/maint/make_page.cgi\">Return to 
the maintenance page</A></STRONG></P>",
        '<H1 ALIGN="center">Make a student page</H1>',
        start_form, 
        '<TABLE><TR><TD ALIGN="right">',
        b('Teacher:'),
        '</TD><TD>',

And so on. This demonstrates another Perl idiom that seems to show up a lot in my CGI scripts: long chains of arguments to the join function. I often use long join statements, connecting (via \n, or some other suitable joining string) a long list of form elements and HTML embellishment. I tend to use single quotes to enclose the HTML, which saves me from having to backslash all the embedded double quotes surrounding the HTML attributes. This means I can’t interpolate variables into the strings, but that’s okay with me because I just terminate the single-quoted string, throw in a comma, and add the variable as another element in that long chain of join arguments. This works nicely for CGI.pm functions, which can’t easily be interpolated inside double-quoted strings the way variables can.

I also sometimes ...