#!/usr/bin/perl
$dir = "./test";
opendir(DIR,$dir) || die "NO SUCH Directory: $dir\n$!";

foreach $zips (readdir DIR){
    $new_name = $zips;
    $new_name =~ s/\.log/\.txt/ig;
    rename ("$dir/$zips","$dir/$new_name") unless ($zips eq $new_name);
}
close(DIR);