(replying to self, duh)
Here is a more complete regex:

sub url_segments {
  local($_) = @_;
  my $segments = { url => $_ };
  my @matches = m{
    \A
    (?:
      ([a-z]{3,6})                # proto
      :
      (?: // )?
    )?
    (?:
      (?:
        ([a-z0-9_-]+)             # user
        (?: : ([^@]+) ) @         # password
      )?
      ( [a-z0-9._-]+ )            # domain
      (?: : (\d+) )?              # port
    )
    (?:
      ( .*? / )                   # location
      (
        ( [^/]*? )                # filename_only
        ( ( \. \w*[a-z]\w* )* )   # ext
      )
      (?: \? ( .* ) )?            # query
    )?
    \Z
  }xi;
  return unless @matches;
  my @parts = qw(proto user pass domain port location
    filename filename_only ext query);
  $matches[$_] and
    $segments->{$parts[$_]} = $matches[$_] for 0 .. $#parts;
  $segments
}
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