my %freq;
for my $i ( 1 .. @data ) {
	$freq{ $1 }[ $-[0] ] += 1/@data while $data[ $i-1 ] =~ /(.)/g;
}

##</code><code>##

my $inc = 1 / @data;                                       ## do the invariant once:
for ( @data ) {                                            ## $_ aliases each line in turn avoids both the $i-1 and indexing the array
    $freq{ $1 }[ $-[0] ] += $inc while /(.)/g;             ## the regex engine operates directly on the $_ alias.
}

##</code><code>##

for( @data ) {                                 ## use $_ to alias the lines
    my $p = -1;                                ## Allow pre-increment which is more efficient
    $freq{ chop() }[ ++$p ] += $inc while $_;  ## implicit arg for chop; avoid call to length.
}