perlでサブルーチンの引数を参照（渡す）する2つの方法

# Before we do the processing, let's print them out and see what they look like
print "In main program before calling subroutine:i=". "@i\n";
print "In main program before calling subroutine:j=". "@j\n";

# Then we process it through the subroutine
reference_sub(@i,@j);
print "In main program after calling subroutine:i=". "@i\n";
print "In main program after calling subroutine:j=". "@j\n";
# Here is the subroutine
sub reference_sub
{
 my (@i,@j)=@_;
 print "In subroutine:i=". "@i\n";
 print "in subroutine:j=". "@j\n";
 # Here we are using pop, and shift for @_
 push(@i,'4');
 shift(@j);
}

# Here are two arrays
my @i =('1','2','3');
my @j =('a','b','c');

# Before we do the processing, let's print them out and see what they look like
print "In main program before calling subroutine:i=". "@i\n";
print "In main program before calling subroutine:j=". "@j\n";

# Then we process it through the subroutine
reference_sub(\@i,\@j);# where we add the backslash, or pass byreference (pass byreference, translated in chapter 6 of the Big Camel book)
print "In main program after calling subroutine:i=". "@i\n";
print "In main program after calling subroutine:j=". "@j\n";
# Here is the subroutine
sub reference_sub
{
 my ($i,$j)=@_;# references are also a special form of data, they are stored as scalar variables in @_
 print "In subroutine:i=". "@$i\n"; So here when we refer to them, we add two symbols in front of them, @ for this is an array and $ for it is a secondary reference.
 print "in subroutine:j=". "@$j\n";
    print "In subroutine:the third element is $$j[2]\n";# When referencing an element in the array the first $$ and the subsequent j[2] represent the third element in the array, while the second $$ represents the secondary reference
 # Here we use pop, and shift for @_
 push(@$i,'4');
 shift(@$j);
}