>perl -wMstrict -le
"my $s = 'abcxyzdef';
 my $exclude = qr{ xyz }xms;
 my $all_not_xyz = qr{ (?! $exclude) . }xms;
 my @matches = $s =~ m{ ($all_not_xyz+) }xmsg;
 print qq{@matches};
"
abc yzdef

##</code><code>##

>perl -wMstrict -le
"my $s = 'abcxyzdef';
 my $exclude = qr{ xyz }xms;
 my @matches = split m{ $exclude }xms, $s;
 print qq{@matches};
"
abc def

##</code><code>##

>perl -wMstrict -le
"my $s = 'abcFOOdefBARghi';
 my $exclude = qr{ FOO | BAR }xms;
 my $all_but = qr{ (?! $exclude) . }xms;
 my @matches = $s =~ m{ ($all_but+) }xmsg;
 print qq{@matches};
 @matches = split m{ $exclude }xms, $s;
 print qq{@matches};
"
abc OOdef ARghi
abc def ghi