#!/usr/bin/env perl

use strict;
use warnings;

my @tests = ('0', '1', '000', '101', '010', '1 * 0 = 0');

my $format = '%9s | ' x 4 . "\n";

printf $format => qw{initial boundary start/end assign};

for (@tests) {
    my ($init, $bound, $start, $assign) = ($_) x 4;
    $bound =~ s/\b0\b/1/;
    $start =~ s/^0$/1/;
    $assign = 1 if $assign == 0;
    printf $format => $init, $bound, $start, $assign; 
}

##</code><code>##

  initial |  boundary | start/end |    assign | 
        0 |         1 |         1 |         1 | 
        1 |         1 |         1 |         1 | 
      000 |       000 |       000 |         1 | 
      101 |       101 |       101 |       101 | 
      010 |       010 |       010 |       010 | 
Argument "1 * 0 = 0" isn't numeric in numeric eq (==) at ./pm_example.pl line 16.
1 * 0 = 0 | 1 * 1 = 0 | 1 * 0 = 0 | 1 * 0 = 0 |