Mastering Perl/Tk

pTk Special Variables and Exporter Symbols

Before we get to the interesting stuff, we need to list the special variables and symbols unique to Perl/Tk.

Global Variables

These global variables are available for your use:

$Tk::VERSION

The Perl/Tk version, which incorporates the Tcl/Tk version it’s based upon, plus the Perl/Tk subrelease number. '800.023' is the 23rd Perl/Tk release based on Tcl/Tk 8.0. '803.xxx' will be based on Tcl/Tk 8.3.

$Tk::library

The pathname where the Tk modules are installed; for example: /usr/local/lib/perl5/site_perl/5.6.0/i686-linux/Tk.

$Tk::platform

The platform, which is 'MSWin32' for Win32 machines, otherwise 'unix'.

$Tk::version

The base Tcl/Tk version, for example '8.0'.

$Tk::patchLevel

The Tcl/Tk patch level, for example '8.0'.

$Tk::strictMotif

A flag to force Tk to use pure Motif style windows.

Symbols Exported by Default

The use Tk statement exports these subroutines by default:

DoOneEvent

Handles Tk events. See Chapter 15.

Ev

Used in callback definitions to delay argument evaluation. See Chapter 15.

exit

Overrides Perl’s CORE::exit to clean up Tk data structures.

Exists($widget)

Ensures that $widget is a valid Perl/Tk widget reference.

MainLoop

Starts the Tk event loop.

tkinit(@args)

Shorthand for MainWindow->new(@args).

Optionally Exported Symbols

You can import these symbols if desired:

catch

Executes a block of code, trapping and ignoring any errors. The code should be enclosed in a Perl block: catch {$widget->cget(-state)} ...