$inst->files(module[, string[, dir[,...]]])
Returns list of filenames. Parameters are:
- module
Required. The name of a module; returns a list of all filenames in
the package. For a list of core files, use the special module name Perl.
- string
Optional. Possible values are prog, man, or all to
return program files, manual files, or all files, respectively.
- dir
Optional. One or more directories. If specified, only filenames under the
specified directories are returned.