What he did is perform another loop, with each iteration happening everytime the regex matched in the string...
Ala

@test = ('foobarfoo', 'blahbarblah', 'bazbarbarbarbaz');

while (@test) {
#
# $_ has foobarfoo or blahbarblah or bazbarbarbarbaz
#
   while(/bar/g) {
#
# matched bar once in foobarfoo inc by 1 
# matched bar once in blahbarblah inc by 1
# matched bar 3 times in bazbarbarbarbaz inc by 1 3 times
#
      $count++;
      print "$count so far\n";
   }
}
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Edit: Sorry for replicating information, Enlil and myself were probably typing at the same time..


/* And the Creator, against his better judgement, wrote man.c */