The while part isn't what sets pos, it's the /g modifier on a match. Simply say: 
$_ = "abcdmefg";
m/m/g;
print "Matched 'm' at ", pos, "\n";

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If you don't need to match a full regex, you can use the index or rindex functions.

In reply to Re: position of the last match in RE by chromatic
in thread position of the last match in RE by Anonymous Monk

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