c:\@Work\Perl>perl -wMstrict -le
"use Data::Dump qw(pp);
 ;;
 my $s = 'abCdefC';
 print '01234567';
 print $s;
 print '------------';
 ;;
 while ($s =~ / (f)*? C /gx) {
   printf qq{matched (f) of %s then C at pos of %d \n},
     pp($1), pos $s;
   }
 ;;
 print '------------';
 ;;
 while ($s =~ / (f*?) C /gx) {
   printf qq{matched (f) of %s then C at pos of %d \n},
     pp($1), pos $s;
   }
"
01234567
abCdefC
------------
matched (f) of undef then C at pos of 3
matched (f) of "f" then C at pos of 7
------------
matched (f) of "" then C at pos of 3
matched (f) of "f" then C at pos of 7