Net::SFTP::Foreign allows you to access remote files as local ones through the SFTP protocol:

use Net::SFTP::Foreign;
use Net::SFTP::Foreign::Constants qw(SSH2_FXF_WRITE SSH_FXF_READ);

my $sftp = Net::SFTP::Foreign->new('user@remote-host');
$sftp->error and die "unable to connect to remote host: ".$sftp->error
+;

my $fh = $sftp->open("remote/file/path", SSH2_FXF_WRITE|SSH2_FXF_READ)
  or die "unable to open remote file: ". $sftp->error;

seek($fh, 0, 2);
print $fh "append this line to file\n";
close $fh;
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