#!/usr/bin/perl
#↑パスは環境に合わせて書き換えてください

 use CGI qw(-any http);
 $cgi = CGI->new;
 $ttl = q([Studying HTTP] env_with_cgi_pm.cgi);

 for(sort $cgi->http) { $li .= $cgi->li("$_ = $ENV{$_}")  if /^(HTTP_|REMOTE_)/; }

 print $cgi->header(),
       $cgi->start_html($ttl),
       $cgi->h1($ttl),
       $cgi->ul($li),
       $cgi->end_html;