Interrupting a loop

[merrymonk]

I am having trouble with interrupting Perl as it processes a loop with a ‘sleep’ in it.
I am using Perl on a Windows 11 pc.
The included code runs a loop. At the start of the loop is ${INT} which sets a sub to be used if CNTRL-C is used. This sub simply sets the variable $loop_test to zero so that the loop ends.
This test Perl works. However, when I use this is the ‘production’ application, where a sub is also called (this tests if a file has recently being store and then acts on this information) CNTRL-C does not work.
Has any Monk a suggestion as to how this can be made to work?

use strict;
use warnings;
my ($loop_test, $cou);
$loop_test = 1;
$cou = 0;
while($loop_test > 0) {
# something which the lets the user set $loop#_tes to 0
    $SIG{INT} = \&tsktsk;
    sleep(5);
    $cou = $cou +1;
    print "end sleep - count $cou\n";
# sub to do something - for exmaple see if a files mod time has change
+d
}
print "\nEND\n";
sub tsktsk{
    $loop_test = 0;
    print "[tsktsk] called\n";
}

I am using Perl Tk and could have a button which when used has the effect of calling the sub to set a variable to end the loop
My attempts to do this have failed because the button fails to respond.
I seem to remember (it is a few years since I have written any Perl Tk code) that there is some property that can be assigned to a button so that it would work in these circumstances.
However, my searches for this have failed.
Can any Monk point me it the right direction?