A more fully worked example may help:

use strict;
use Tk;

my @booths;

my $mw = MainWindow -> new;
for (0..5) {
    $booths[$_]{button} = $mw->Button (
        -text => "Booth $_",
        -command => [\&Vote, \@booths, $_]
        )->pack ();
}

$mw->Button (-text => 'Done', -command => sub {$mw->destroy ()})->pack
+ ();

MainLoop;


sub Vote {
    my ($boothsRef, $boothNum) = @_;
    
    my $count = ++$boothsRef->[$boothNum]{count};
    $boothsRef->[$boothNum]{button}->configure (-text => "Booth $booth
+Num ($count)");
}
[download]

Note that the thing passed in is actually an array, but it could be a HoH or any other suitable structure.