Unfortunately there is no easy fix for your problem. The issue is that the Windows GUI expects you to pass it control at regular intervals when you're in a loop using:

Win32::GUI::DoEvents();
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However, because you're using Net::Telnet and it's waitfor method, you've handed over control and blocked your entire program until the matching text is detected. Thus everything in your program blocks and your GUI freezes.

For more information see the Win32::GUI faq

You have many options. One is to go through the gymnastics of running the telnet portion of your code in a thread and reading output from it in a loop that calls DoEvents. Or you could just grab a copy of Net::Telnet and modify it to do that internally

Short of developing your own network and telnet code, a wrapper around each blocking call to the Telnet module may be the easiest answer. It could generate and trap and alarm if the code takes too long. If the alarm fires, call DoEvents() and then restart the Telnet operation.

No guarantees that would work of course. It may introduce some subtle timing problems. Would be much cleaner to find an Asynchronous Telnet module to use,or bite the bullet and write your own networking code that doesn't block.