my $line= Filter {chomp} ''.<STDIN>;
[download]

It might be clearer (codewise, and to avoid the need for commentary) to change this to:

my $line= Filter {chomp} readline(STDIN);
[download]

The different MapCar* functions are only different in how they deal with being pqssed

NextPermute sounds cool.

PS> Around line 955: '=item' outside of any '=over'