Performance
Perl lets you do just about whatever you want, and that includes things that may be slow or memory-intensive. Here's how to avoid some of these.
Use while to iterate over files,
not for
Instead of slurping in all lines of a file and then working on the array with for,
read in one line at a time with while.
These two loops are functionally the same:
for ( <> ) {
# do something
}
while ( <> ) {
# do something
}
The difference is that the for reads the entire file into a temporary array, and the while reads one at a time. For small files this may not matter, but for larger ones it may eat up all your available memory.
Using while in this case is just good practice.