Since you're looking for the offset of an exact match, the index function is ideal for you. There's no need to use an escaped regex (which could be done with /\Q$letter\E/).

Also, with a binary file, reading with the diamond op is chancy. You don't know where the audio may have a crlf pair. You clearly want to slurp the whole file into $word, so undefine $/ to make diamond do that. 

my $word = do {
    local $/;
    <WORDSOUND>
};
my $offset = index $word, $letter;

[download]
If you need more sophisticated analysis, take a look at PDL.

After Compline,
Zaxo

In reply to Re: searching for a binary string in a binary file by Zaxo
in thread searching for a binary string in a binary file by rochlin

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