SPUG: Counting the number of instances in a string using Perl's regexes...

[Colin Meyer]

On Mon, Dec 18, 2000 at 11:51:43AM -0800, Jonathan Gardner wrote:
> Say I had a string with a whole bunch of characters - "asdfjkhafjklhaf".
> 
> How would I go about counting the number of individual characters (say,
> 'a')?

$str = 'asdfjkhafjklhaf';

$num_a = $str =~ tr/a/a/;

from perldoc perlop:

       tr/SEARCHLIST/REPLACEMENTLIST/cds

       y/SEARCHLIST/REPLACEMENTLIST/cds
               Transliterates all occurrences of the characters
               found in the search list with the corresponding
               character in the replacement list.  *It returns the
               number of characters replaced or deleted.* ...

also see perldoc perlfaq4 and search for:
How can I count the number of occurrences of a substring within a string? 

-C.

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