use File::Find (); # no namespace pollution
my @startDirectories = ....;
my @foundFiles = &FindFiles(@startDirectories);

sub FindFiles {
  my @rootdirs = @_;
  my @foundFiles = ();

  File::Find::find sub {
    if (-f $File::Find::name){ # just files
      push (@foundFiles, $File::Find::name);
    }
  }, @rootdirs;

  return (@foundFiles);
} # FindFiles