ren *.log *.txt

##</code><code>##

for f in /tmp/*.log ; do mv $f ${f%%.*}.txt; done

##</code><code>##

my @files = File::Find::Rule->file()->name('*.log')->maxdepth(1)->in($destinationDirectory);
foreach my $src ( @files ){
  my $dest = $src; $dest =~ s/[^.]+$/txt/;
  rename $src, $dest;
}