#! perl
use strict;
use warnings;

my $file1 = 'file1.txt';
my $file2 = 'file2.txt';
my $error = 'error.txt';

open(my $in1, '<', $file1) or die "Cannot open file '$file1' for reading: $!";
open(my $in2, '<', $file2) or die "Cannot open file '$file2' for reading: $!";
open(my $out, '>', $error) or die "Cannot open file '$error' for writing: $!";

my $lineno = 1;

while (my $line1 = <$in1>)
{
    my $line2 = <$in2>;

    printf $out "Error:lineno:%d please check mismatch\n", $lineno
        unless $line1 eq $line2;

    ++$lineno;
}

close $out or die "Cannot close file '$error': $!";
close $in2 or die "Cannot close file '$file2': $!";
close $in1 or die "Cannot close file '$file1': $!";