Creating a hash using a function - perl

Question

I am trying to create a hash using a function in perl. Actually i was working on creating a binary search tree in perl. Below is the code :
sub newhash {
$data = shift;
$left = undef;
$right = undef;
%node = ("data"=>$data,"left"=>$left,"right"=>$right);
return (\%node);
}
$firstele = newhash(2);
foreach ( keys %$firstele )
{
print "$_:$firstele->{$_}\n";
}
$node = newhash(1);
foreach ( keys %$node )
{
print "$_:$node->{$_} \n";
}
foreach ( keys %$firstele )
{
print "$_:$firstele->{$_}\n";
}
The trouble is that when i am printing the original hash, the data key gets replaced by whatever i am passing to the newhash function . The output:
left:
right:
data:2
left:
right:
data:1
left:
right:
data:1
Any ideas why is the data key getting replaced?

Answer 1

use strict; would tell you about a bunch of undeclared variables; lexicalize them with my and it should solve your problem. As it stands, there's only one %node and you overwrite it with every call to newhash.
use strict;
sub newhash {
my $data = shift;
my $left;
my $right;
my %node = ( # <-- a brand new %node every time
data => $data,
left => $left,
right => $right,
);
return (\%node); # new %node, new reference
}
my $firstele = newhash(2);
print "firstele data: $firstele->{data}\n";
my $node = newhash(1);
print "node data: $node->{data}\n";
print "firstele data: $firstele->{data}\n";

Answer 2

Here is the code for adding elements in BT structure.
use strict;
use List::Util qw(first);
my (#input,$data);
print "Enter the data for being in a BST structure: ";
$data=<>;
chomp($data);
my $root=$data;
push(#input,$data);
while($data =~ m/\b-?\d{1,3}\b/){
my $idx=first { $input[$_] == $root } 0..$#input;
if($data<$root) {
for(my $i=0;$i<=$idx;$i++) {
next if($data>$input[$i]) ;
if($data<$input[$i]) {
splice(#input,$i,0,$data);
}
last;
}
}
if($data>$root) {
for(my $i=$idx;$i<=$#input;$i++) {
if($data>$input[$i]) {
if(($i+1==scalar(#input)) or ($data<$input[$i+1] && $i+1 !=
scalar(#input))) {
splice(#input,$i+1,0,$data);
last;
}
else {
next;
}
}
last;
}
}
print "Enter the number for being in a BT structure: ";
$data=<>;
chomp($data);
}
print "Final BT Array:\n",join(',', #input),"\n";