Tk is one of the most commonly used GUI toolkits for Perl. Other common toolkits are GTK+2 & 3, WxWidgets, and Win32 widgets. Less commonly used are Qt4, XUL, Prima, and FLTK.
Tk, GTK+3, Wx, Win32, Prima, FLTK, and XUL are actively updated. Qt4 and GTK+2 are no longer developed actively, but ...