The last_choice variable remembers the last choice made from an overload-resolution menu. It is useful primarily in scripts. For example:
function myprint {
# print it twice, once in octal, then in hex
# reuse same overload choice, if any
DBX_output_base=8 builtin print $*
DBX_output_base=16 builtin print $* <<-EOF
$last_choice
EOF
}