my %filter_map = ( ... );

my $filter = q{};
if ($filter_clean) {

    my @filter_split = split //, $filter_clean;

    for my $fc (@filter_split) {
        if ( $fc =~ /\d/ ) {
            $filter .= $fc;
        }
        else {
            $filter .= $filter_map{ uc $fc };
        }
    }
}

say $filter;

##</code><code>##

my %map = ( ... );
$map{$_} = $_ for 0..9;

my $numeric;
for (split //, uc($word)) {
    $numeric .= $map{$_};
}

say $numeric;

##</code><code>##

my %map = ( ... );
$map{$_} = $_ for 0..9;

my $numeric =
    join '',
     map $map{$_}, 
      split //, uc($word);

say $numeric;