If you are talking tcl which if you are in UGS you might be, you could try something like this. This does work, you will get a long string, but the order in which it appends is somewhat hazy. So if the order in which the variables are added to the string, this should work.
foreach {index value} [array get myarray] {
if {![info exists stringvar]} {
set stringvar $value
} else {
append stringvar $value
}
} ;# foreach