OK, for the third, probably one single little change: declare $DELAY with the my function:

#!/usr/bin/perl -w
use strict;
use warnings;
# slowcat - emulate a  slow line printer
# usage: slowcat -DELAY files ...
my $DELAY = ($ARGV[0] =~ /^-(.\d+)/) ? (shift, $1) : 1;
$| = 1;
while (<>) {
    for (slit(//)) {
        print;
        select(undef,undef,undef, 0.005 * $DELAY);
   }
}
[download]

The same correction will apply to most of your other problems.

And BTW, yes, I was fortunate enough to be born with the art of debugging Perl, I was doing that all the time in my cradle or while drinking milk from the breast of my mother (even though this was 30 years before Larry Wall invented Perl, but I knew it all already), but if it is not your case, too bad, you'll have to learn it the hard way: by doing it yourself again and again. You can get some help, and I am ready to help you again on the programs you have shown, but at one point, you really have to do it yourself.