The way I see it, you have a certain orig_name=>new_name mapping (a hash) where $hash{$orig_name}=$new_name. And you wish to replace all orig_name in your log_file with new_name.

#Open the file and slurp it into an array @lines

#Search orig_name in line and replace it with new_name

map{s/$orig_name/$new_name/g} @lines;

#Write the transformed array into file again
[download]