This worked for me. I tried to condense it a little; also, I turned debugging on:

#!/usr/bin/perl

use strict;
use warnings;
use Net::SFTP;
use YAML;
use YAML::Dumper;

my $host = 'localhost';
my $user = 'user';
my $pass = 'password';

eval {
    $SIG{ALRM} = sub { die "Net::SFTP timed out\n" };
    alarm 2;
    my $sftp = Net::SFTP->new(
        $host,
        user     => $user,
        password => $pass,
        debug    => 1,
    );

    my $dumper = YAML::Dumper->new;
    $dumper->indent_width(4);
    print $dumper->dump( $sftp->ls('/usr/lib/perl5') );
};
if ($@) {
    chomp $@;
    die "Error: $@ trying to connect to CMS\n";
}
else {
    print "All done!\n";
}
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