#!/usr/bin/perl 

print "Search for what: ";
chomp(my $search = <STDIN>);
@words = split(/ /, $search);

# Turn words into regular expressions
@words = map {qr/$_/i} @words;

# If you don't want the user to have to
# worry about regex syntax, use this instead:
# @words = map {qr/\Q$_/i} @words

open(DATA, "books.txt") or die "error opening file $!";

while (<DATA>) {
        $matches=0;
        foreach $word(@words) {
                if ($_ =~ $word) {
                        print unless ($matches > 0);    
                        $matches++;                     
                }
        }
}