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

while ( (print "Enter Date: "), 
        (my $date =<STDIN>) !~ /^\s*q(uit)?\s*$/i  
      )
{
    next if $date =~ /^\s*$/; # reprompt on blank line
    chomp($date);

    if ($date =~ m|[^\d/]|)
    {
       print "Valid date has only digits and /!\n";
       next;
    }
    
    #....more valdiation here ....
    
    #then actually do something before reprompting
    
}

##</code><code>##

my $start_date;
my $end_date;

while (print "Enter start date: ",!start_date_ok(<STDIN>));
while (print "Enter end date: ",  !end_date_ok  (<STDIN>));