my %formats = (
   "item_name"  => 15, # where 15 is the length
   "item_name2" => 20,
   # etc.
);

# code removed for demonstration

$c = correct_length($c,'item_name');

sub correct_length {
    my ($string,$item) = @_;
    $string .= ' ' unless length($string) >= $formats{$item};
    return($string);
}