Perl : 用 Hook::LexWrap 在函数调用前、后加临时操作

见 mastering perl : chapter 3 perl debuggers
#!/usr/bin/perl
use Hook::LexWrap qw/wrap/;
wrap add,
    pre => sub { print "get arguments : @_\n" },
    post => sub { print "return value : $_[-1][0]\n" }
    ;
print "the sum : ", add(1, 2) , "\n";
sub add {
    my ($n, $m) = @_;
    return $n+$m;
}
#get arguments : 1 2 ARRAY(0xdd4cb8)
#return value : 3
#the sum : 3