#!/usr/bin/perl  
use strict; 
use warnings; 
 
print "Enter nr of users: "; 
my $nr = <>; 
 
my @a; 
 
for (1 .. $nr) { 
    print "Enter name of user nr $_\n"; 
    my $name = <>; 
    chomp $name; 
    push @a, $name; 
} 
 
# pieces of the MAC regex 
my $d = "[0-9A-Fa-f]"; 
my $dd = "$d$d"; 
 
my $max_tries = 3; 
 
for my $i ( 0 .. $#a ) { 
    my $tries = 0; 
    LOOP: { 
        print "Enter MAC address for user $a[$i]\n"; 
        my $mac = <>; 
        chomp $mac; 
 
        if ( $mac =~ /^$dd([:;-])$dd(\1$dd){4}$/ ) { 
            print "$a[$i] has MAC $mac\n"; 
        } 
        else { 
            $tries++; 
            if ( $tries < $max_tries ) { 
                print "False MAC, try again.\n"; 
                redo LOOP; 
            } 
            else { 
                print "Too many false tries. Bye.\n"; 
                exit; 
            } 
        } 
    } 
}