($nth_chunk) = $text =~ /(?:PREFACE(MATCH)POSTFIX){N}/;

##</code><code>##

my ($number13) = $text =~ /(?:<TD nowrap>(.*?)</TD>\n){13}/;

##</code><code>##

"abcdef" =~ /(.)/;   # $1 is "a"
"abcdef" =~ /(.)+/;  # $1 is "f"