Thank you very much for your rapid response. As was the case with BrowserUK's response, I tried to adapt your suggestion to a subroutine I could easily drop into my test program.

sub _rolf_recognize_limited_urls {
  my ($input, $max) = @_;
  my @captures = ();
  @captures[0..$max-1] = split /,(?=https?:)/, $input, $max+1;
  return [ @captures ]; 
}
[download]

As was the case with BrowserUK's formulation, the first two of four tests failed. I only got all four tests to past when I grepped for definedness:

sub _rolf_recognize_limited_urls {
  my ($input, $max) = @_;
  my @captures = ();
  @captures[0..$max-1] = split /,(?=https?:)/, $input, $max+1;
  return [ grep { defined($_) } @captures ];
}
[download]

Thank you very much.

Jim Keenan