How can I make a filehandle local to a subroutine? How do I pass filehandles between subroutines? How do I make an array of filehandles?

    local(*FH);

But while still supported, that isn't the best to go about getting local filehandles. Typeglobs have their drawbacks. You may well want to use the FileHandle module, which creates new filehandles for you (see the FileHandle manpage):

    use FileHandle;
    sub findme {
        my $fh = FileHandle->new();
        open($fh, "</etc/hosts") or die "no /etc/hosts: $!";
        while (<$fh>) {
            print if /\b127\.(0\.0\.)?1\b/;
        }
        # $fh automatically closes/disappears here
    }

Internally, Perl believes filehandles to be of class IO::Handle. You may use that module directly if you'd like (see Handle), or one of its more specific derived classes.

Once you have IO::File or FileHandle objects, you can pass them between subroutines or store them in hashes as you would any other scalar values:

    use FileHandle;

    # Storing filehandles in a hash and array
    foreach $filename (@names) {
        my $fh = new FileHandle($filename)              or die;
        $file{$filename} = $fh;
        push(@files, $fh);
    }

    # Using the filehandles in the array
    foreach $file (@files) {
        print $file "Testing\n";
    }

    # You have to do the { } ugliness when you're specifying the
    # filehandle by anything other than a simple scalar variable.
    print { $files[2] } "Testing\n";

    # Passing filehandles to subroutines
    sub debug {
        my $filehandle = shift;
        printf $filehandle "DEBUG: ", @_;
    }

    debug($fh, "Testing\n");