You could toss the various values into arrays. Something tht may help is:

use warnings;
use strict;

my @fields;

my $fieldValue = 'Grand'; # Given name field contents
push @fields, [$fieldValue, 10]; # 20 character wide field

$fieldValue = 'Father'; # Sir name
push @fields, [$fieldValue, 10]; # 25 character wide field
push @fields, ['007 Bond Street', 15];
push @fields, ['Wibble Wobble', 15];
push @fields, ['', 15];
push @fields, ['Erewhon', 15];
#...

my $record = join '', map {sprintf "%-*.*s", $_->[1], $_->[1], $_->[0]
+} @fields;

print $record;
[download]

Prints:

Grand     Father    007 Bond StreetWibble Wobble                 Erewh
+on
[download]

which ties the field size to the field contents at the point where the contents are added to the field list then uses the field size to control field width in a sprintf later on.