You can also use sub prototypes to help make things pretty. They'll give you some argument checking capability, and will convert your arrays into refs for you. Here's a simple example:

my @foo = qw(123 456 789);
my @bar = qw(abc def ghi);

sub qux(\@\@*)
{       print join "\t", @_, "\n";

        my $foo = shift;
        my $bar = shift;

        print "foo: ", join "\t", @$foo, "\n";
        print $FH "bar: ", join "\t", @$bar, "\n";
}

qux(@foo, @bar, 'STDERR');
print "\n";
print \@foo . "\t" . \@bar;
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Applying this to your code, we get something like (notice how clean the subroutine call is):

# the filehandle name must be quoted if you have strict subs enabled.
process(@data,@set_up,$template, 'OUT');

# Process
sub process (\@\@$*) {
    my $data_ref = shift();
    my $set_up_ref = shift();
    my $template = shift; #For unpack
    my $FH = shift; # The * gets us a handle reference

    foreach my $record (@data) {
        --do things--}
}
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Check out perlsub's section on prototypes for more info.

Update: Of course protoypes are a bit controversial...

TGI says moo