Is there a way of taking, say,

/(\d\s+foo)[^\r\n]*(\d\s+foo)/
[download]

What about:

my $re = qr/\d\s+foo/;
sub match {
  local $_ = shift;
  /(\d\s+foo)[^\r\n]*\1/x       and print "1\n";
  /\d\s+foo  [^\r\n]*\d\s+foo/x and print "2\n";
  /($re)     [^\r\n]*\1/x       and print "3\n";
  /$re       [^\r\n]*$re/x      and print "4\n";
}
match '4  foo4  foo';   ## easily matched
match '4  foo5  foo';   ## a bit trickier

__OUTPUT__

1
2
3
4
2
4
[download]

We can see that all 4 regexps matched the first text but in order to match the second, we can't use the backreference and must resort to other things. I think isolating the common part and using it where necessary ("4") is best.