task
Essentially, count the number of occurrences of =={{header| on each task page.

Output:

100 doors: 20 examples.
99 Bottles of Beer: 29 examples.
Abstract type: 10 examples.

Total: X examples.
For a full output, updated periodically, see Rosetta Code/Count examples/Full list.

You'll need to use the Media Wiki API, which you can find out about locally, here, or in Media Wiki's API documentation at, API:Query

import httpclient, strutils, xmltree, xmlparser, cgi
 
proc count(s, sub: string): int =
  var i = 0
  while true:
    i = s.find(sub, i)
    if i < 0: break
    inc i
    inc result
 
const
  mainSite = "http://www.rosettacode.org/mw/api.php?action=query&list=categorymembers&cmtitle=Category:Programming_Tasks&cmlimit=500&format=xml"
  subSite = "http://www.rosettacode.org/mw/index.php?title=$#&action=raw"
 
var client = newHttpClient()
var sum = 0
for node in client.getContent(mainSite).parseXml().findAll("cm"):
  let t = node.attr("title").replace(" ", "_")
  let c = client.getContent(subSite % encodeUrl(t)).toLower().count("{{header|")
  echo t.replace("_", " "), ": ", c, " examples."
  inc sum, c
 
echo "\nTotal: ", sum, " examples."