sub LTR {
    # 116 characters
    my@a;for(@_){if(/\d/){push@a,$_}else{$/=pop@a;
    $,=join' ',pop@a,$_,$/;$,=~s/(.*)/($1)/ if((/[+-]/);push@a,$,;$;=$_}}@a
}
print LTR qw(1 2 - 3 4 + 5 * /);