Eulerian path, directed graph - perl

Question

Good evening. I'm really a beginner, and I am working in an implementation of an Eulerian path. That means that every edge (not a vertex) of a directed graph has to be used only once.
For some reason it doesn't manage to go over all vertices even if in paper it should. It seems to ignore half of the vertices or simply not adding them to the circuit.
The expected outcome is:
6->7->8->9->6->3->0->2->1->3->4
Nevertheless, the outcome I get is:
6 6 6 6 6 6 6 7 7 7 7 7 7 7 8 8 8 8 8 8 8 9 9 9 9 9 9 9 3 3 3 3 3 3
What i have as code is the following:
my %edges={'6'=>['3','7'],'8'=>['9'],'1'=>['3'],'0'=>['2'],'3'=>['0','4'], '7' =>['8'],'9'=>['6'],'2'=>['1']};
my $startvertex=6; #this i got from additional code
my $location=$startvertex;
my #stack = ($startvertex);
my #circuit = ();
while (#stack)
{
if (#{$edges{$location}}[0])
{
push #stack, $location;
my $newlocation=#{$edges{$location}}[0];
splice #{$edges{$location}},0,1;
$location=$newlocation;
}
else
{
push #circuit, $location;
$location=pop #stack;
}
}
my #revcircuit= reverse #circuit;
print #revcircuit;
Thank you very much in advance for your insight.

Answer 1

The problem is here:
if (#{$edges{$location}}[0])
One of your nodes is called 0 which is false in Perl. Therefore, once the zero node is reached, the program continues as if there were no more nodes.
Use defined instead.
Here's a working version, slightly edited (e.g. removed unnecessary array dereference):
#!/usr/bin/perl
use warnings;
use strict;
my %edges = ( 6 => [3, 7],
8 => [9],
1 => [3],
0 => [2],
3 => [0, 4],
7 => [8],
9 => [6],
2 => [1]);
my $startvertex = 6;
my $location = $startvertex;
my #stack = ($startvertex);
my #circuit;
while (#stack) {
if (defined $edges{$location}[0]) {
push #stack, $location;
$location = shift #{ $edges{$location} };
} else {
push #circuit, $location;
$location = pop #stack;
}
}
my #revcircuit = reverse #circuit;
print "#revcircuit\n";
Also note that it uses round parentheses to define the %edges hash. Curly braces introduce a hash reference, with them I'm getting
Reference found where even-sized list expected at ./1.pl line 5.