use warnings;
use strict;
my $str='XtestXYtest2';
my $BRK = qr(X|Y|^|$)i;
my @pieces = $str =~ /($BRK+)(.+?(?=$BRK))/gsp;
push @pieces,${^POSTMATCH} if ${^POSTMATCH};
print "INTENDED: These were the phrases (and breaks) extracted:\n",join("\n",@pieces),"\n-------\n";
$BRK = qr(^|X|Y|$)i;
@pieces = $str =~ /($BRK+)(.+?(?=$BRK))/gsp;
push @pieces,${^POSTMATCH} if ${^POSTMATCH};
print "WRONG: These were the phrases (and breaks) extracted:\n",join("\n",@pieces),"\n";