RFC 283 (v1) C<tr///> in array context should return a histogram

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=head1 TITLE

C<tr///> in array context should return a histogram

=head1 VERSION

  Maintainer: Simon Cozens <[email protected]>
  Date: 24 Sep 2000
  Mailing List: [email protected]
  Number: 283
  Version: 1
  Status: Developing

=head1 ABSTRACT

C<tr///> in array context should return a histogram explaining the
number of matches for each letter in the pattern.

=head1 DESCRIPTION

This has been on the Perl 5 to-do list for ages and ages. The idea is
that when you're transliterating a bunch of things, you want to know
how many of each of them matched in your original string.

For instance, while C<tr/x//> will count the x's, C<tr/xy//> will count
both x's and y's - you don't know how many of each. So, the proposal is
that C<tr> in the array context should return a hash, like this:

    (%foo) = "xyzzy" =~ tr/xyz//

    # %foo is ( x => 1, y => 2, z => 3);

=head1 IMPLEMENTATION

I posted a patch to Perl 5.6 to do this some time back; it's a very
simple matter of constructing the hash and incrementing the values every
time you do a transliteration of a character. Of course, since we don't
know what Perl 6's transliteration operator's going to look like, it's
hard to know how to implement an extension to it...

=head1 REFERENCES

None.