use strict;
use warnings;

my $data = do {local $/; <DATA>};

while ($data =~ /^(john.*)\n(?:(?!john).*\n)*?(jacob.*)/mg) {
	print "$1 > $2\n";
}

__DATA__
bhgfsggdsgsg
--
john1
weruwearnwrnweuarar
jjafdaiuweifweofiuwe
jacob - 1.0
--
nfaslf23523525
john2
asfsjldf43tgre
john3
asbdfhskafbv3333v
sdfahh34ttg
sadfhk34t3wtg
sdfhk3gfwghhw3
jacob - 2.0