c:\@Work\Perl\monks>perl -wMstrict -le
"my $str = qq{cat\nman\ncat\ndog\neel\nman\nman\ncat\ncat\nman\n};
 ;;
 my $sub_str = qq{cat\nman\n};
 my $n = 3;
 ;;
 $str =~ s{ (\Q$sub_str\E) }{ join '', map qq{$_ $1}, 1 .. $n }xmsge;
 print qq{>$str<};
"
>1 cat
man
2 cat
man
3 cat
man
cat
dog
eel
man
man
cat
1 cat
man
2 cat
man
3 cat
man
<

##</code><code>##

c:\@Work\Perl\monks>perl -wMstrict -le
"my $str = qq{cat\nman\ncat\ndog\neel\nman\nman\ncat\ncat\nwoman\n};
 ;;
 my $sub_str = qr{ cat \n (?: wo)? man \n }xms;
 my $n = 3;
 ;;
 $str =~ s{ ($sub_str) }{ join '', map qq{$_ $1}, 1 .. $n }xmsge;
 print qq{>$str<};
"
>1 cat
man
2 cat
man
3 cat
man
cat
dog
eel
man
man
cat
1 cat
woman
2 cat
woman
3 cat
woman
<