Just a flashback from the past...

     #!/usr/bin/awk -f
     # wordfreq.awk --- print list of word frequencies
     {
         $0 = tolower($0)    # remove case distinctions
         # remove punctuation
         gsub(/[^[:alnum:]_[:blank:]]/, "", $0)
         for (i = 1; i <= NF; i++)
             freq[$i]++
     }
     
     END {
         for (word in freq)
             printf "%s\t%d\n", word, freq[word]
     }
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