Are you sure this is the most efficient way to do this?

Yes, I am quite sure.

  1. tr doesn't make copies, it operates in-place.
  2. It is optimised internally to recognise that when the source and replacements are identical, it is in 'counting mode' only.

For multi-character substring counting avoid creating the huge list:

$s = 'ab'x 10e6;;

++$n while $s=~ m[ab]g;;
print $n;;
10000000

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In reply to Re^5: Out of Memory by BrowserUk
in thread Out of Memory by Michael Kittrell

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