if ($ARGV[0] =~ /^ep_svr_
                 (\d)      # any single-digit number -- use  (\d+) for multi-digits
                 _([A-Za-z]{3})  # three letters
                 _([A-Za-z]{3})  # three letters
                 _(\w)     # any "word" character -- use (.) for any character
                 \z         # if you want to anchor the end
               /x) {
   print "matched ",$ARGV[0],"\n";
   my ($num,$alpha1,$alpha2,$char) = ($1,$2,$3,$4);
   # Do something with the captured parts here...
}