10. Block arg to function 

sub mygrep (&@) {
    my($coderef, @args) = @_;

    my @results;
    foreach (@args) {
        my $string = uc($_);
        local($_) = $string;
        push @results, $string if $coderef->($string);
    }
    return @results
}

say join ', ', mygrep {
    length($_) > 3
} ('Tom', 'Dick', 'Larry');       # DICK, LARRY