perl -d
  DB<1> $_ = "This is list number 12. It contains apples, pears, peach
+es. Total cost is 5.";
  DB<2> x /(?:It contains\s+|\G)(?:([^,.\s]+)[,.]\s)/g
0  'apples'
1  'pears'
2  'peaches'
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Starting after 'It contains ', this captures anything that isn't a dot, comma, or space that is followed by a dot or comma followed by space. Requiring that a space follows the matched dot or comma eliminates '5.' from the results.