For that matter, why not the following (using just the CPAN modules)?

# Almost no testing, so be warned...
perl -Mstrict -Mwarnings -MCPAN -le '
CPAN::HandleConfig->load;
CPAN::Shell::setup_output;
CPAN::Index->reload;
CPAN::HandleConfig::edit( q{prerequisites_policy follow}, );
my @tk_modules = grep { $_->id =~ m/^\bTk\b(?:::.*)?$/i; } 
    CPAN::Shell->expand( q{Module}, q{/./}, );
foreach my $mod ( @tk_modules ) {
    print qq{Attempting install of }, $mod->id;
    CPAN::Shell->install($mod);
}
'
[download]

Hope that helps.

Update: 2019-01-30 - Changed regex from /^\bTk\b/i to /^\bTk\b(?:::.*)?$/i to get only Tk and Tk::* modules.