my $string = "
start:
end:

test
code
start: real
1
end: real
with
start: real
repeating newlines
and more than
start: real
one

instance
end: real
of the 
start: real
desired
string


end: real


start:
end:";

if ($string =~/(start: real)((.|\n)*(?!start: )(.|\n)*)*(end: real)/){
	print "$&";
	}