Controlling a Multistage CGI Script
The next interesting
section of the script is a long
chain of
unless-elsif
blocks that test the
contents of the $action
variable, and execute
various subroutines based on what’s in there. The idea here is
to have a single CGI script that will carry out a whole sequence of
actions as a user clicks his way through multiple dynamically
generated pages, with the passed action
parameter
controlling which part of the script is run for each invocation:
unless ($action) { &show_links; } elsif ($action eq 'show_student_form') { &show_student_form; } elsif ($action eq 'show_leader_form') { &show_leader_form; } elsif ($action eq 'Create student page') { &post_student_page; } elsif ($action eq 'Create leader page') { &post_leader_page; } elsif ($action eq 'regenerate_site_links') { ®enerate_site_links; } else { $err_msg = "<LI>Wacky 'action' param '$action'. Shouldn't be able to get here."; }
I’ve had people tell me that my use of
unless-elsif
is evil, but it makes sense to me
when I read it out loud. Your mileage may vary.
The overall gist of this script is that each
unless-elsif
block will load up the
$content
variable with a different page to be
delivered back to the requesting user. If anything goes wrong, a
descriptive error message will be stuck in the
$err_msg
variable. After all the
unless-elsif
stuff is done, the script will check
for the presence of anything in $err_msg
, and if something is there, it will create an HTML error message incorporating ...
Get Perl for Web Site Management now with the O’Reilly learning platform.
O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.