my $in_file = 'b2bclient-gateway-heartbeat.log'; open my $in_fh, '<', $in_file or die "Could not open file $in_file: $!"; my $out_file = 'output.txt'; open my $out_fh, '>', $out_file or die "Could not open file $out_file: $!"; while ( my $line = <$in_fh> ) { print {$out_fh} $line if $line =~ /TWO/; } close $in_fh or die "Could not close file $in_file: $!"; close $out_fh or die "Could not close file $out_file: $!";