[texhax] Last char of a string

[Michael Barr]

Is there any easy way to find the last character of a string?

Why?  Well the online journal I do the tex editing for uses runin 
subsection titles.  They have to end with a period or other punctuation. 
So I want to look at the last character of the title and add a period 
unless it already is a period (or question mark or even an exclamation 
point).

Michael Barr