# 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--} }