print $mac =~ 
/^([0-9A-Z]{1,2}):([0-9A-Z]{1,2}):([0-9A-Z]{1,2}):([0-9A-Z]{1,2}):([0-9A-Z]{1,2}):([0-9A-Z]{1,2})$/
0 0A 0C B B8 F

##</code><code>##

print $mac =~ /^(?:([0-9A-Z]{1,2}):){5}([0-9A-Z]{1,2})$/
B8 F

##</code><code>##

print $mac =~ /^(?:([0-9A-Z]{1,2}):){2}([0-9A-Z]{1,2}):([0-9A-Z]{1,2}):([0-9A-Z]{1,2}):([0-9A-Z]{1,2})$/
0A 0C B B8 F