Disclaimer: It's been five or six years since I used Perl on OpenVMS so my information may not be up to date. I'm relying on my memory which is not quite as good as it used to be.

When you say that the DecTerm window "freezes", do you mean that no input or output is displayed? Or no input is accepted but the output is displayed properly? I assume from what you said that you can ctrl-Y out of the program.