$ cat foo.pl
#!/usr/bin/env perl
use strict;
use warnings;
use Data::Dump qw(pp);

my $t = <DATA>;
my ($nV, $nE) = split /\s+/,$t;

# read graph
my %G;
my ($src, $dst);
while (<DATA>) {
    next if /^\s+$/;
    ($src, $dst) = split /\s+/;
    last if !$nE--;
    $G{$src}{$dst}=0;
    $G{$dst} = {} if ! exists $G{$dst};
}

print pp(\%G),"\nStart: $src, End: $dst\n\n";

__DATA__
5 6
1 2
2 3
2 4
4 5
1 3
3 5
1 5

$ perl foo.pl
{
  1 => { 2 => 0, 3 => 0 },
  2 => { 3 => 0, 4 => 0 },
  3 => { 5 => 0 },
  4 => { 5 => 0 },
  5 => {},
}
Start: 1, End: 5