I think you had better add some word boundries in there to avoid catching words that start or end with "sp".

use Data::Dumper;
$string = "sp Hello there sp \n Hey hey sp How are you? sp I need a ds
+p chip and have a spelling test.";
@results = $string =~ m/\bsp\s+(.*?)\s+sp\b/g;
print Data::Dumper->Dump([\@results]);

__OUTPUT__

$VAR1 = [
          'Hello there',
          'How are you?'
        ];
[download]

--

flounder