#!/usr/bin/env perl
use warnings;
use strict;
use Text::CSV;
use Graph;

my $filename = 'input.csv';

my $g = Graph->new(directed=>1);

open my $fh, '<', $filename or die "$filename: $!";
my $csv = Text::CSV->new({ binary=>1, auto_diag=>2, eol=>$/ });
while ( my $row = $csv->getline($fh) ) {
	my ($author1, $author2, $interactions) = @$row;
	$g->set_edge_attribute( $author1, $author2, # auto-creates edge
		'interactions', $interactions );
}
$csv->eof or $csv->error_diag;
close $fh;

for my $e ($g->edges) {
	my ($author1, $author2) = @$e;
	next if $g->has_edge($author2, $author1);
	my $interactions = $g->get_edge_attribute( $author1, $author2,
		'interactions' );
	$csv->print(select, [ $author1, $author2, $interactions ]);
}