I wrote Net::SSH2::Cisco but never had Nexus switches to test on. It could be a lot of things, including the prompt string. From the CRAPPS utility I wrote:

... has an issue with prompt discovery on new Cisco IOS-XR 
   routers. These routers have a prompt like:

      RP/0/RP1/CPU0:routername#

    The current Net::Telnet::Cisco prompt matching will not catch 
    this and cause timeouts on Telnet connects to these types of 
    routers.

    This script sends a new prompt that should match existing 
    prompts and the new IOS-XR prompts. If you are having failed 
    connect issues when in Telnet mode, but logging shows that 
    you are connecting, the custom prompt is the first place to 
    look.

    Net::Telnet::Cisco supplied prompt:

      '/(?m:^[\w.-]+\s?(?:\(config[^\)]*\))?\s?[\$#>]\s?(?:\(enable\))
+?\s*$)/'

    Updated by this program:

      (?:[\w.\/]+\:)?

    inserted after the "'/(?m:^" The rest of the line is left as is.
[download]

Note that I wrote Net::SSH2::Cisco as a drop in replacement for Net::Telnet::Cisco, so the same above should apply.

my $t = Net::SSH2::Cisco->new(
    [...]
    prompt => '/(?m:^ [...] s*$)/'; # or whatever matches your prompt
);
[download]

Also agree with zentara; waitfor_clear shouldn't need to be messed with, but if you're going to, at least us integer 0 (not '0' string).