e.g. {append x bar}     -> foobar

proc sum args {expr [join $args +]}
e.g. {sum 1 2 3} -> 6
#native sum2 {function (interp, args) {return eval(args.join("+"));}}
#e.g. {sum2 2 3 4} -> 9

e.g. {catch foo msg} -> 1
e.g. {set msg} -> {invalid command name "foo"}
e.g. {catch {expr 7*6}} -> 0
e.g. {catch {expr 7*6} msg; set msg} -> 42

e.g. {concat {a b} {c d}} -> {a b c d}

e.g. {set d [dict create a 1 b 2 c 3]} -> {a 1 b 2 c 3}
e.g. {dict exists $d c} -> 1
e.g. {dict exists $d x} -> 0
e.g. {dict get $d b}    -> 2
e.g. {dict keys $d}     -> {a b c}

e.g. {set x 0xFF; expr {$x+0}} -> 255
e.g. {expr 0376}               -> 254
e.g. {set x 0375; expr $x}     -> 253
e.g. {expr {$x}}   -> 253
e.g. {expr 6 * 7}  -> 42
e.g. {expr 1 == 2} -> 0
e.g. {expr 1 < 2}  -> 1
e.g. {expr 1 > 2}  -> 0
e.g. {expr 1 != 2} -> 1
e.g. {expr 1 <= 2} -> 1
e.g. {expr 1 >= 2} -> 0
e.g. {expr !0}     -> 1
e.g. {expr !42}    -> 0
e.g. {set x 3}     -> 3
e.g. {expr $x+1}   -> 4
e.g. {expr {$x+1}} -> 4
e.g. {set x a; set y b; expr {$x == $y}} -> 0
e.g. {expr {$x != $y}} -> 1
e.g. {expr 43 % 5}     -> 3 
e.g. {set x -44; expr {-$x}} -> 44
e.g. {expr 1<<3} -> 8

set forres ""
e.g. {for {set i 0} {$i < 5} {incr i} {append forres $i}; set forres} -> 01234
e.g. {foreach i {a b c d e} {append foreachres $i}; set foreachres}   -> abcde

e.g. {format %x 255} -> ff
e.g. {format %X 254} -> FE

e.g. {llength $x}         -> 4
e.g. {lindex $x 2}        -> c
e.g. {lrange $x 1 2}      -> {b c}
e.g. {lreverse {a b c}}   -> {c b a}
e.g. {lsearch $x b}       -> 1
e.g. {lsearch $x y}       -> -1
e.g. {lsort {z x y}}      -> {x y z}

e.g. {proc f args {expr [join $args +]}} -> ""
e.g. {f 1}     -> 1
e.g. {f 1 2}   -> 3
e.g. {f 1 2 3} -> 6

e.g. {regexp {X[ABC]Y} XAY}    -> 1
e.g. {regexp {X[ABC]Y} XDY}    -> 0
e.g. {regsub {[A-C]+} uBAAD x} -> uxD 

e.g. {split "a b  c d"}     -> {a b {} c d}
e.g. {split " a b  c d"}     -> {{} a b {} c d}

e.g. {string length ""}       -> 0
e.g. {string length foo}      -> 3
e.g. {string range hello 1 3} -> ell
e.g. {string tolower Tcl}     -> tcl
e.g. {string toupper Tcl}     -> TCL
e.g. {string trim " foo "}    -> foo

e.g. {set x a.\x62.c} -> a.b.c ;# severe malfunction, breaks test suite operation :(

puts "total $total tests, passed $passed, failed $fail"
#----------- clean up variables used in tests
foreach var [info vars] {
    set pos [lsearch $vars $var] ;# expr can't substitute commands yet
    set neq [string compare $var vars]
    if {$var != "vars" && $pos < 0} {unset $var}
}
unset vars var pos neq
puts "vars now: [info vars]"
puts "[llength [info commands]] commands implemented"