#!perl -wl

use strict;

$_ = "[ABC AB AB12/83]";
print "I have a string like this\n$_";
s{\[([A-Z_]+)\s([A-Z_]+)\s([A-Z_]+)(\d+)/(\d+)\]}{$1_$2_$3$4_$5};
print "I would like to end up with\n$_";