$string = "I have 5 apples, 6 oranges, and 8 limes.";

#Match the oranges only if they are more than the apples
#and fewer than the limes.
$string =~ m/(\d+)\sapples.*(\d+)\soranges.*(\d+)\slimes(?{if (($1<$2) && ($2<$3))})/g;