within

#!/usr/bin/perl -w

# Print all lines from stdin that are in (or not in, with -v) the files
# named as arguments.
#
# This could be done with fgrep -x (slower) or comm (requires that all
# inputs be pre-sorted). It does require more memory since all the lines
# in the named files need to be placed in a hash.

use Getopt::Std;

my %seen = ();
my %opts;

getopts('vj:', \%opts);

while (<>) {
    $seen{$_} = 1;
}

while (<STDIN>) {
    my $this_line = $opts{j} ? (split)[$opts{j}-1]."\n" : $_;
    print if $seen{$this_line} xor $opts{v};
}