'''Morse en/decoder''': works both ways ASCII <-> Morse
======
  proc morse {s} {
    # \u00C4 - Ä (Auml)
    # \u00D6 - Ö (Ouml)
    # \u00DC - Ü (Uuml)
    set _morse {
        A ._ \u00C4 ._._ B _... C _._. D _.. E . F .._.
        G __. H .... I .. J .___ K _._ L ._.. M __
        N _. O ___ \u00D6 ___. P .__. Q __._ R ._. S ...
        T _ U .._ \u00DC ..__ V ..._ W .__ X _.._ Y _.__ Z __..
        0 _____ 1 .____ 2 ..___ 3 ...__ 4 ...._ 5 .....
        6 _.... 7 __... 8 ___.. 9 ____.
        . ._._._ , __..__ ? ..__.. / _.._. ( _.__. ) _.__._
        + ._._. : ___... ; ...___ - _...._ = _..._
        ~ ._... # ..._._ $ _..._._ 
    }
    set res ""
    if [regexp {^[._ ]+$} $s] {
        regsub -all {  +} $s " B " s
        foreach i [split $s] {
            if {$i==""}  continue
            if {$i=="B"} {append res " "; continue}
            set ix [lsearch $_morse $i]
            if {$ix>=0} {
                append res [lindex $_morse [expr {$ix-1}]]
            } else {append res ?}
        }
    } else {
        foreach i [split [string toupper $s] ""] {
            if {$i==" "} {append res "  "; continue}
            set ix [lsearch -exact $_morse $i]
            if {$ix>=0 && $ix%2==0} {
                append res "[lindex $_morse [expr {$ix+1}]] "
            }
        }
    }
    set res
  } ;#RS - slightly uncrufted 2001-12-04
======

[KBK] (2002-04-09) 
 QST QST QST DE KE9TV/2 KE9TV/2 KE9TV/2 BT
added punctuation, plus added procedural signs
 ~ - Stand by (AS)
 # - End of work (SK or VA)
 $ - Break (BK)
Procedural signs '''AR''', '''BT''' and '''KN''' are encoded by '''+''', '''=''' and '''(''' respectively, since those are the meaning of those signs within a message body.

Ampersand should be sent as the two characters '''ES'''.

Still to do: '''AAA''' is a period, but a decimal point is sent as a character '''R'''.
 VY 73 DE KE9TV/2 SK AR
----
For practizing, see also [A little Morse trainer]
----
[DKF]: Here's a morse code player I wrote for Rosetta Code that uses [Snack] to do the playing:
======
# This uses the GUI-free part of the Snack library
package require sound
 
# A simple pause while running the event loop, in terms of basic time units
proc pause n {
    global t
    after [expr {$t * $n}] set ok 1
    vwait ok
}
# Generate using a sine-wave filter
proc beep n {
    global frequency
    set f [snack::filter generator $frequency 30000 0.0 sine -1]
    set s [snack::sound -rate 22050]
    $s play -filter $f
    pause $n
    $s stop
    $s destroy
    $f destroy
    pause 1
}
# The dits and the dahs are just beeps of different lengths
interp alias {} dit {} beep 1
interp alias {} dah {} beep 3
 
set MORSE_CODE {
    "!" "---."         "\"" ".-..-."        "$" "...-..-"        "'" ".----."
    "(" "-.--."         ")" "-.--.-"        "+" ".-.-."        "," "--..--"
    "-" "-....-" "." ".-.-.-"        "/" "-..-."
    ":" "---..." ";" "-.-.-."        "=" "-...-"        "?" "..--.."
    "@" ".--.-." "[" "-.--."        "]" "-.--.-"        "_" "..--.-"
    "0" "-----"         "1" ".----"        "2" "..---"        "3" "...--"
    "4" "....-"         "5" "....."        "6" "-...."        "7" "--..."
    "8" "---.."         "9" "----."
    "A" ".-"         "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" "--.."
}

# The code to translate text to morse code and play it
proc morse {str wpm} {
    global t MORSE_CODE
    set t [expr {1200 / $wpm}]
    # Backslash and space are special cases in various ways
    set map {"\\" {} " " {[pause 4]}}
    # Append each item in the code to the map, with an inter-letter pause after
    foreach {from to} $MORSE_CODE {lappend map $from "$to\[pause 3\]"}
    # Convert to dots and dashes
    set s [string map $map [string toupper $str]]
    # Play the dots and dashes by substituting commands for them
    subst [string map {"." [dit] "-" [dah]} $s]
    return
}

# We'll play at a fairly high pitch 
set frequency 700
 
morse "Morse code with Tcl and Snack." 20
======
----
[Arts and crafts of Tcl-Tk programming]