#!/usr/bin/env perl
use 5.010; use warnings; use strict;

while(<DATA>){
    print;                               # print the line
    if(/banana/){                        # if it contained banana
        print scalar <DATA> for 1..3;    # print the next three lines
        print "This line was added.\n";  # then add the new line
    }
}                                        # then print the rest of the lines
__DATA__
a is for apple
b is for banana
c is for cantaloupe
d is for dill
e is for elderberry
f is for fennel
g is for grapefruit
h is for honeydew