Either of these should be 7 to 8 times faster than your original. They're much the same on my machine, with the latter winning on later perls:

my %freq;
my $inc = 1 / @data;
for my $d ( @data ) {
#    $freq{ substr $d, $_, 1 }[ $_ ] += $inc for 0 .. length( $d )-1;
    my $p = 0;
    $freq{ chop $d }[ $p++ ] += $inc while length $d;
}

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In reply to Re: Weighted frequency of characters in an array of strings by BrowserUk
in thread Weighted frequency of characters in an array of strings by K_Edw

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