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

my $answer = ask_yes_no ("Gimme a Yes or No!(Y/N)?");
print "answer = $answer\n";

sub ask_yes_no
{
    my $prompt = shift;
    
    while ( (print $prompt), 
            (my $answer = <STDIN>) !~ /^\s*q(uit)?\s*$|^\s*abort\s*?/i   
          )
    {
       next if $answer =~ /^\s*$/;  # re-prompt on blank line
       
       $answer =~ s/^\s*//;  #no leading spaces
       $answer =~ s/\s*$//;  #no trailing spaces
       $answer = uc $answer;  
       return $answer if ($answer eq 'Y' or $answer eq 'N');
       
       print "Illegal entry try again..!!\n";       
    }
    
    die "quit or abort was entered! **Abort Program!!**\n";    
}

__END__
Example: UI test run....

C:\TEMP>perl askyn.pl
Gimme a Yes or No!(Y/N)?2345
Illegal entry try again..!!
Gimme a Yes or No!(Y/N)?y
answer = Y

C:\TEMP>perl askyn.pl
Gimme a Yes or No!(Y/N)?N
answer = N

C:\TEMP>perl askyn.pl
Gimme a Yes or No!(Y/N)?a
Illegal entry try again..!!
Gimme a Yes or No!(Y/N)?ABORT
quit or abort was entered! **Abort Program!!**

C:\TEMP>perl askyn.pl
Gimme a Yes or No!(Y/N)?Q
quit or abort was entered! **Abort Program!!**

C:\TEMP>perl askyn.pl
Gimme a Yes or No!(Y/N)?
Gimme a Yes or No!(Y/N)?
Gimme a Yes or No!(Y/N)?
Gimme a Yes or No!(Y/N)?