Many thanks to all... so far I've got this lovely chunk o'code:

# format for fixed-length line:
    my $filebegin_format = "%-1.1s%-8.8s%-6.6s%-17.17s%-25.25s%-16.16s
+%-1.1s%-9.9s%-9.9s%-8.8s%-35.35s%-25.25s%-2.2s%-12.12s%-3.3s"; #file 
+layout for characters 1-177
    my $request_format = "%-4.4s%-4.4s%-1.1s%-1.1s%-35.35s%-35.35s%-35
+.35s%-25.25s%-2.2s%-12.12s%-3.3s%-4.4s"; #file layout for requests 1-
+8 
    my $request9_format = "%-6.6s%-4.4s%-4.4s%-1.1s%-1.1s%-1.1s%-35.35
+s%-35.35s%-35.35s%-25.25s%-2.2s%-12.12s%-3.3s%-4.4s"; #file layout fo
+r request 9
    my $fileend_format = "%-5.5s%-1.1s%-16.16s%-4.4s%-25.25s%-16.16s%-
+9.9s%-1.1s%-40.40s%-14.14s%-2.2s%-9.9s%-3.3s%-3.3s%-10.10s%-40.40s%-2
+2.22s%-1.1s"; #file layout for characters 1630-1850
    my $format = $filebegin_format . $request_format . $request_format
+ . $request_format . $request_format . $request_format . $request_for
+mat . $request_format . $request_format . $request9_format . $fileend
+_format;
    
# build fixed-length line:
    $fl_line = sprintf $format, $filetype, $batch, $serial, $sys_time,
+ $t_lastname, $t_firstname, $t_mi, $t_mi, $ssn, $ssn_cor, $dob, $t_ad
+dress, $t_city, $t_state, $t_zip, $t_country, $code_1, $date_1, $type
+_1, $priority_1, $addressee_1, $institution_1, $address_1, $city_1, $
+state_1, $zip_1, $country_1, $filler, $code_2, $date_2, $type_2, $pri
+ority_2, $addressee_2, $institution_2, $address_2, $city_2, $state_2,
+ $zip_2, $country_2, $filler, $code_3, $date_3, $type_3, $priority_3,
+ $addressee_3, $institution_3, $address_3, $city_3, $state_3, $zip_3,
+ $country_3, $filler, $code_4, $date_4, $type_4, $priority_4, $addres
+see_4, $institution_4, $address_4, $city_4, $state_4, $zip_4, $countr
+y_4, $filler, $code_5, $date_5, $type_5, $priority_5, $addressee_5, $
+institution_5, $address_5, $city_5, $state_5, $zip_5, $country_5, $fi
+ller, $code_6, $date_6, $type_6, $priority_6, $addressee_6, $institut
+ion_6, $address_6, $city_6, $state_6, $zip_6, $country_6, $filler, $c
+ode_7, $date_7, $type_7, $priority_7, $addressee_7, $institution_7, $
+address_7, $city_7, $state_7, $zip_7, $country_7, $filler, $code_8, $
+date_8, $type_8, $priority_8, $addressee_8, $institution_8, $address_
+8, $city_8, $state_8, $zip_8, $country_8, $filler, $code_9, $date_9, 
+$type_9, $exception_9, $priority_9, $addressee_9, $institution_9, $ad
+dress_9, $city_9, $state_9, $zip_9, $country_9, $filler, $bill_total,
+ $cc_type, $cc_number, $cc_exp, $cc_name, $cur_lastname, $cur_firstna
+me, $cur_mi, $cur_address, $cur_city, $cur_state, $cur_zip9, $cur_pco
+de, $cur_country, $phone, $email, $filler, $reject;
    
    my $asr_line = uc($fl_line); #make the line uppercase
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Which so far is giving me just what I need. And should be fairly simple to update when the client changes their minds again. Thanks to all!