perl-tk (Tk graphical interface for Perl) Perl/Tk is an extension for writing Perl programs with a Graphical User (GUI) on both Unix and Windows 95/NT. Tk was originally developed as an extension to the Tcl language, for use with the X Window System on Unix. With its port to Perl, Tk gives Perl programmers the same control over a graphical desktop that Tcl programmers have taken for granted.