Thanks, yes, I saw that in the doc about CF_TEXT; but the same doc also states that CF_UNICODETEXT is a constant that's "not recognized by Win32:Clipboard," which is untrue. So I was hoping the doc was wrong here, as well, and that there was an easy way around the issue.
Options 2 and 3 are more than I care to dig into right now. But since I'm using Win32::GuiTest I might also look into using its WMSetText method to write the text directly to the textarea, instead of going through the clipboard. Wish me luck!