c:\@Work\Perl>perl -wMstrict -le
"my @array = qw(PAT  PATxPATxPAT  PATxPATxPATxPATxPAT  xxxxx);
 ;;
 my $acc;
 do { my $count = () = s/PAT/REP/g;  $acc += $count; } for @array;
 ;;
 print qq{\$acc: $acc   \@array: (@array)};
"
$acc: 4   @array: (REP REPxREPxREP REPxREPxREPxREPxREP xxxxx)