I had it in mind to pass a string and a character to a subroutine, and within the subroutine, use a variable ("$char", below) containing the character as follows:

<kbd>$count = $string =~ tr/$char/$char/;</kbd>

Purpose: get a count of occurrences of "$char" within "$string".

In which case, tr/// happily counts occurrences of "c" and "h" and "a" and "r"...just as I told it to do. :)  Can a variable be used in this instance? I realize that s/// can be used; it will be less efficient than tr///--so I understand--but it will return a count, given the right syntax.

Slightly off-topic: in perlop (ActiveState's, at least), the following appears in the section on tr///:
   Options:
      c    Complement the SEARCHLIST.
Just below that, the following appears:
   If the /c modifier is specified, the SEARCHLIST character set is complemented.

Aspiring technical writers everywhere, please study the above for a moment for an example of how not to write documentation--whether it's end-user documentation, or "only" reference material.</rant>

In reply to Using variables with tr/// by greenhorn

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