For completeness, here's how to do it on Windows:

use strict;
use Win32::Console;

my $CONSOLE = Win32::Console->new();

my ($width, $height) = $CONSOLE->Size();
# $CONSOLE->Size(80, 25); # force a console size

print "Console size is $width x $height\n";
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Note that if the user resizes the window after the call to new(), the Size() method will not return the new size. If your application needs to handle resizing, it should create the Win32::Console object each time it needs to read the size.