c:\@Work\Perl\monks>perl -wMstrict -le
"use 5.010;
 ;;
 my $data = '1|2|3|4|5|6|7|8|9|a|b|c|d|e|f|g|h|i';
 print qq{'$data'};
 ;;
 local our $n;
 $data =~ s{ \| (?(?{ ++$n < 10 || $n > 12 }) (*FAIL)) }{ pipe }xmsg;
 print qq{'$data'};
"
'1|2|3|4|5|6|7|8|9|a|b|c|d|e|f|g|h|i'
'1|2|3|4|5|6|7|8|9|a pipe b pipe c pipe d|e|f|g|h|i'

##</code><code>##

c:\@Work\Perl\monks>perl -wMstrict -le
"my $data = '1|2|3|4|5|6|7|8|9|a|b|c|d|e|f|g|h|i';
 print qq{'$data'};
 ;;
 use constant O => 10;
 use constant T =>  3;
 ;;
 my $p = $data =~ tr/|//;
 my $n = $p - O - T + 1;
 my $m = $n + T - 1;
 $data =~ s{ [|] (?= (?: [^|]* [|]){$n,$m} [^|]* \z) }{ pipe }xmsg;
 print qq{'$data'};
"
'1|2|3|4|5|6|7|8|9|a|b|c|d|e|f|g|h|i'
'1|2|3|4|5|6|7|8|9|a pipe b pipe c pipe d|e|f|g|h|i'