[pm-h] substitution with increment

[Russell L. Harris]

I have several dozen groups of files; each group consists of one to
several hundred files.  

Within each group, the bash "ls" command lists the files in proper
order, because the filename includes a multi-character identifier
(such as 43-29, 43-30, 44-01, 44-02, etc.).

I need to add to the file names within each group a file number, such
that the files may be referenced in proper order as 001, 002, 003,
etc.  It is important that the file number contain exactly three
digits.

I am making other changes to the filename, and I have been able to
accomplish everything (undoubtedly crudely) with the diamond operator
and the substitution operator s/// (using the "g" suffix).  But I have
not figured out a reasonable scheme for adding the sequential file
number.  Can this be done with s/// ?

RLH