As a pieced of additional information, if you're learning Perl/Tk, I suggest you run, do not walk, over to the TkDocs Site and peruse their Tk Tutorial. Because Tk has been around so long, there are many ways to generate interfaces. Many of these ways have been supplanted by newer, better ways that better fit with the underlying operating system user interface guidelines for your particular platform.

The Tk Tutorial is current, up to date, and as a bonus gives you direct comparisons with Tcl, Perl, Python, and Ruby.