Subroutines problem

I want to pass two array into the subroutine, but it doesn't work.

the correct result:
-------------------------
first: 1,2,3
second: a,b,c
pre: 1,2,3
pos: a,b,c

How can I correct it? Thanks!!!


the result after running:
-------------------------
first: 1,2,3
second: a,b,c
pre: 1,2,3
pos: 1,2,3


the perl script here:
---------------------

#!/usr/bin/perl

$first[0]=1;
$first[1]=2;
$first[2]=3;

$second[0]="a";
$second[1]="b";
$second[2]="c";

print "first: $first[0],$first[1],$first[2]\n";
print "second: $second[0],$second[1],$second[2]\n";

&testing(@first,@second);

sub testing {
my @pre=@_;
my @pos=@_;
print "pre: $pre[0],$pre[1],$pre[2]\n";
print "pos: $pos[0],$pos[1],$pos[2]\n";
}

---------------------

I think the answer to your question lies in the use of references. Try reading the tutorials here at DevShed (in the Perl section) or try rading the perlref manpage for more gritty details.

Use references to send arrays to the program. What your program does is send @first and @second, and then stores both in @pre. Insead send the addresses of the arrays to the subroutine, and then dereference them.


#!/usr/bin/perl

$first[0]=1;
$first[1]=2;
$first[2]=3;

$second[0]="a";
$second[1]="b";
$second[2]="c";

print "first: $first[0],$first[1],$first[2]\n";
print "second: $second[0],$second[1],$second[2]\n";

&testing(\@first,\@second);

sub testing {
my $x=$_[0];
my $y=$_[1];

@pre = @$x;
@pos = @$y;

print "pre: $pre[0],$pre[1],$pre[2]\n";
print "pos: $pos[0],$pos[1],$pos[2]\n";
}