Your question sounds odd of where Perl is used in s/w testing. It all depends on your Application/Testing Environment.
Suppose, your application is generating lots of files into a particular directory and you want to check for a particular string which is present in each and every file without actually opening all the files ( It's a tedious job to open,check for the string and increment the count :rolleyes: )
You can write an automated perl script which opens all the files,search for the string and display the result which can save your lot of effort.
I remember the module Test::Files will do it for you.