wusphere pay no attention to the one liner above, it's wrong, and off the point of your original question, as was pointed out offline .. brackets don't belong in tr///, should be looking for digits not anything else like a-z .. 
perl -e '$str="fff123"; $fu = $str =~ tr/0-9//c; print $fu,"\n";'

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Which is what Zaxo said anyway.

In reply to Re^2: count digit in a numeric value by hsinclai
in thread count digit in a numeric value by wusphere

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