Wikipedia trivia: if you take any article, click on the first link in the article text not in parentheses or italics, and then repeat, you will eventually end up at "Philosophy".

wikipedia-philosophy-loop.pl

#!/usr/bin/perl

use strict;
use warnings;
use Switch;

use LWP::Simple qw($ua);
# changing User Agent string because Wikipedia.org blocks default LWP::Simple User Agent
$ua->agent("WikiBot/0.1");

my $startWord = $ARGV[0];

# argument: name of a wikipedia article, result: name of another wikipedia article
sub getFirstLink { my $pageName = shift;
  my $url = "http://en.wikipedia.org/w/index.php?title=Special:Export&pages=$pageName&offset=1&limit=1&action=submit";
  my $str = LWP::Simple::get($url);
  
  if ($str =~ m/<text[^>]*>(.*)<\/text>/s) {
    my $content = $1;
    # avoiding text from parentheses, boxes and image captions...
    my ($braces,$brackets,$parens)=(0,0,0);
    while ($content =~ m/(\[\[|\]\]|\(|\)|{|})/g) {
      switch ($1) {
        case '(' { $parens++; }
        case ')' { $parens--; }
        case '{' { $braces++; }
        case '}' { $braces--; }
        case '[[' { 
        if ($parens == 0 && $braces == 0 && $brackets == 0) {
          my $pos = pos($content);
          if (substr($content,$pos,5) ne "File:" && substr($content,$pos,6) ne "Image:") {
            pos($content)=$pos-2;
            $content =~ m/\[\[([^\]\|]+)(\|[^\]\|]+)?\]\]/g;
            return $1;
          }
        }
        $brackets++;
        }
        case ']]' { $brackets--; }
      }
    }
  } else {
    print "ERROR on '$pageName': unable to find any links on this page, or the keyword does not exist!\n\n";
    return 0;
  }
}

my $myWord = $startWord;
my @words = ();

while($myWord) {
  # filling word list for loop detection
  push @words, $myWord;
  
  #printing word
  print "--> $myWord\n";
  
  $myWord = getFirstLink($myWord);
  if ( grep { $_ eq $myWord} @words ) {
    # printing last word and exiting when loop was detected
    print "--> $myWord\n";
    print "##### loop detected!";
    push @words, $myWord;
    last;
  }
}