Can't locate in @INC

Install an old library lightsquid on Ubuntu 20.04. When visit the cgi, internal server error pops up.

Debug the cgi by directly run it in /var/www/lightsquid:

/var/www/lightsquid$ perl index.cgi
Can't locate in @INC (you may need to install the CGI module) (@INC contains: /etc/perl /usr/local/lib/x86_64-linux-gnu/perl/5.30.0 /usr/local/share/perl/5.30.0 /usr/lib/x86_64-linux-gnu/perl5/5.30 /usr/share/perl5 /usr/lib/x86_64-linux-gnu/perl/5.30 /usr/share/perl/5.30 /usr/local/lib/site_perl /usr/lib/x86_64-linux-gnu/perl-base) at index.cgi line 19.
BEGIN failed--compilation aborted at index.cgi line 19.

Seems that some modules are missing, after several search:

Combined with the error message:

$ apt install libcgi-pm-perl

Then it works:

/var/www/lightsquid$ perl index.cgi
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

  <META name="robots" content="noindex,nofollow">
  <META name="generator" content="LightSquid -">
  <META http-equiv="Content-Type" content="text/html; charset=US-ASCII">