With a pattern of /ou/ and numlines set to 3 I get:

 perl -ne '$x=/ou/..0; print if $x && $x-1 <= 3' data.dat
[download]

As in:

% cat data.dat
one
two
thrtestee
four
five
six
werwr
werwer
seen?

% perl -ne '$x=/ou/..0; print if $x && $x-1 <= 3' data.dat

four
five
six
werwr
[download]

Notice how it prints the matching line plus an additional $numlines lines...

-Blake