use strict;
use warnings;
use Data::Dumper;

print join " ", splitter('xx((556xx');

sub splitter {
  local $_ = shift;
  split /
  		 (?<!^)									#not preceeded by start of string.
  		 (?! 									#not followed by...
  		 	(??{ 
  		 		quotemeta substr($_, $-[0]-1, 1) 	# the escaped (quote-metad) last character of the last match.
  		 										# note: $-[0] is the offset of start of last successful match.
  		 										# $-[1] (not used here) would be the offset of start of the first sub pattern.
  		 	   })
  		 )
  		 /x;      
}