Program Repair Shop

Useless variables

Let's look at these two lines together:

        my $usage = "NO ARGS!
        This perl script finds all duplicate files by content, not file name
        usage: $0 <options to find>
        example: $0 . -mount\n\n";
        die $usage if @ARGV == 0;

This is the only place where $usage is used
This is an unusually surprising example of Use immediately follows assignment
When a variable is assigned, used once immediately, and never again, it can often be eliminated
As here; why not just:

        die "NO ARGS!
        This perl script finds all duplicate files by content, not file name
        usage: $0 <options to find>
        example: $0 . -mount\n\n"
                if @ARGV == 0;

Or perhaps:

        @ARGV > 0 or die "...";