Problem Statement

Morse code is one of the simplest and most versatile methods of telecommunication in existence. It has been in use for more than 175 years — longer than any other electronic encoding system.

Send a string as audible Morse code to an audio device   (e.g., the PC speaker).

As the standard Morse code does not contain all possible characters, you may either ignore unknown characters in the file, or indicate them somehow   (e.g. with a different pitch).

Let's start with the solution:

#!/bin/sed -rf
# Convert to uppercase
s/.*/\U&/
# Add lookup table
s/$/\nA.-B-...C-.-.D-..E.F..-.G--.H....I..J.---K-.-L.-..M--N-.O---P.--.Q--.-R.-.S...T-U..-V...-W.--X-..-Y-.--Z--../
# Main loop
:a
s/([A-Z])([^\n]*\n.*\1([-.]+))/\3 \2/
ta
# Remove lookup table
s/\n.*//


$ echo hello world! | ./morse.sed 
.... . .-.. .-.. ---  .-- --- .-. .-.. -.. !