find unique or common lines between two files

ediff.pl

#!/usr/bin/perl -w
# Time-stamp: <2004-04-02 14:37:41 Tao Liu>

use strict;

if (@ARGV>0 and $ARGV[0] eq "-h") {
    print "ediff : compute two sets with \'or diff and\'. \nUsage:\tediff [-h] : help, this info\n\tediff A or B : union of two sets\n\tediff A diff B : elements in
 A but not in B\n\tediff A and B : intersection of two sets\n";
    exit;
}

die "ediff needs _EXACTLY_ three paras!\nediff [-h] to get help...\n" if (@ARGV!=3);

open (IN1,"$ARGV[0]") || die "cannot open $ARGV[0]:$!\n";
open (IN2,"$ARGV[2]") || die "cannot open $ARGV[2]:$!\n";

if ("or" eq $ARGV[1]) {
    #my %in1;
    #my %in2;
    my %out;
    while(<IN1>) {
	chomp;
	$out{$_}=1;
    }
    while(<IN2>) {
	chomp;
	$out{$_}=1;
    }
    foreach (keys %out) {
	print "$_\n";
    }
} elsif ("diff" eq $ARGV[1]) {
    #my %in1;
    my %in2;
    my %out;
    while(<IN2>) {
	chomp;
	$in2{$_}=1;
    }
    while(<IN1>) {
	chomp;
	$out{$_}=1 if(not exists $in2{$_});
    }
    foreach (keys %out) {
	print "$_\n";
    }
} elsif ("and" eq $ARGV[1]) {
    my %in1;
    #my %in2;
    my %out;
    while(<IN1>) {
	chomp;
	$in1{$_}=1;
    }
    while(<IN2>) {
	chomp;
	$out{$_}=1 if(exists $in1{$_});
    }
    foreach (keys %out) {
	print "$_\n";
    }


} else {
    print "\"$ARGV[1]\" is not a recognized command!\nediff [-h] to get help...\n" ;
    exit;
}

close IN1;
close IN2;