If I have the input files
file1.txt:

1.he is man
2.don't you
3.xyzzy
4.what goes on
[download]

he is
z
what are
try to do
[download]

# pm_11118096_1.pl                                          15jun20waw

use strict;
use warnings;

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

open my  $h2, '<', $file2 or die "cannot open file2";

my @a2 = <$h2>;
close $h2;
chomp @a2;
my $match = join '|', @a2;
$match = qr/$match/;

open my $f3,'>',"do.txt" or die "$!";
open my $h1, '<', $file1 or die "cannot open file1";
my @a1 = <$h1>;
close $h1;

print grep {$_ !~ $match} @a1;
# print $f3 grep {$_ !~ $match} @a1;
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c:\@Work\Perl\monks\Sidd@786>perl pm_11118096_1.pl
2.don't you
4.what goes on
[download]

If I comment out the
    # print grep {$_ !~ $match} @a1;
line and uncomment the
    print $f3 grep {$_ !~ $match} @a1;
line, I get an output file do.txt with the content

2.don't you
4.what goes on
[download]

When you run your code with these input files, what do you get?

Perhaps your algorithm is wrong or perhaps your data isn't what you think it is. Here is an SSCCE:

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

my @a2 = qw/foo bar baz/;
my $match = join '|', @a2;
my @a1 = qw/bar quux/;
print grep {$_ !~ $match} @a1;
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This prints one blank line (for "bar") and one line with "quux" in it. Do you understand why?

Amended thanks to AnomalousMonk for pointing out the error.

This prints one blank line (for "bar") ...

I don't understand this. I get the "quux" line, but I get no blank line. Capturing the output of the grep in an array and then dumping it shows only one item.

---

Give a man a fish:  <%-{-{-{-<

    #use strict;
use warnings;

 $file1 = 'C:/Users/Siddharth/Desktop/our.txt';
 $file2 = 'C:/Users/Siddharth/Desktop/my.txt';

open  $h2, '<', $file2 or die "cannot open file2";

 @a2 = <$h2>;
close $h2;
chomp @a2;
 $match = join '|', @a2;
$match = qr/$match/;

open  $f3,'>',"C:/Users/Siddharth/Desktop/one.txt" or die "$!";
open  $h1, '<', $file1 or die "cannot open file1";
my @a1 = <$h1>;
close $h1;

#print grep {$_ !~ $match} @a1;
 print $f3 grep {$_ !~ $match} @a1;
[download]

when i run the above code, it is showing the error-undefined variable $file1.please help me

  $file1 = \<<"END1";
he/is/man/reg[30]
what/goes/on/reg[32]
i_am_a_man
you_are_reg[60]
END1

my $file2 = \<<"END2";
/is/man/reg[30]
are_reg[60] 
try/to/do/reg[65]
you/reg[31]
END2

 
  
   open(my $f3, ">", "C:/Users/Siddharth/Desktop/two.txt")
    or die "Can't open < input.txt: $!";
open  my $h2, '<', $file2 or die "cannot open file2";
my %map = <$h2>;

my ($regex) = map { qr/$_/ }          # 2.
    join '|', map {quotemeta}
    close $h2;


open  my $h1, '<', $file1 or die "cannot open file1";
my @a1= <$h1>;   


 

#print grep {$_ =~ $regex} @a1;
 
print $f3  grep {$_ !~ $regex} @a1;
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