#!/usr/bin/perl -w
use strict;

# How many fabrics are you using?

my $number_of_fabrics;

print "How many fabrics are you using? \n";

chomp($number_of_fabrics = <STDIN>);

$number_of_fabrics =~ s/\D//; # only allow number input

## $number_of_fabrics ||= 3;  # assume default quietly

unless($number_of_fabrics and $number_of_fabrics >=3 )
{
    warn "Ahem!!! You must enter a NUMBER >= 3, but that's ok, default is 3";
    $number_of_fabrics = 3;
}
#... more to come ... ;D