Match groups so you can split it up into scheme, username, password, host, port, path, query, fragment. Not difficult to approximate, though for best results with diverse schemes you’d want an engine that allows repeated named groups, and I don’t know if any do (JavaScript and Python don’t).

Python's `regex` package does allow repeated named group.

I mean ya that would match a query string, but it wouldn't parse it?

I assume they meant "some regex implementation, including replace and/or match groups".

Like, for just the params part (yes, broken and simplistic):

  #!/usr/bin/perl
  $_="a=b&c=d&e=f&whatever=some thing";
  while (s/^([^&]*)=([^&]*)(&|$)//) {
    print "[$1] [$2]\n";
  }