To trim lines based on line number in perl - perl

Question

My Perl file generates the text file which usually contains 200 lines. Sometimes it exceeds 200 lines (For example 217 lines). I need to trim off the rest of the lines from the 201st line. I have used the counter method to trim the exceeded lines. Is there any other simple and efficient way to do this?
Code:
#!/usr/bin/perl -w
use strict;
use warnings;
my $filename1="channel.txt";
my $filename2="channel1.txt";
my $fh;
my $fh1;
my $line;
my $line1;
my $count=1;
open $fh, '<', $filename1 or die "Can't open > $filename1: $!";
open $fh1, '>', $filename2 or die "Can't open > $filename2: $!";
while(my $line = <$fh>)
{
chomp $line;
chomp $line1;
if($count<201)
{
print $fh1 "$line\n";
}
$count++;
}
close ($fh1);
close($fh);

Answer 1

I have already mentioned in my comment, this is short version of that comment If you actually trying to trim the file you can use the Perl One Liner instead of writing the whole code
perl -pe 'last if($. == 201);' input.text >result.txt
-p used for process the file line by line an print the output
-e execute flag, to execute the Perl syntax
With Perl script you can do this also
open my $fh,"<","input.txt";
open my $wh,">","result.txt";
print $wh scalar <$fh> for(1..10);

Answer 2

xxfelixxx already gave you the correct answer. I am just changing my earlier posted answer, to clean up your code and to write back to the original file:
use strict;
use warnings;
my #array;
my $filename="channel.txt";
open my $fh, '<', $filename or die "Can't open > $filename: $!";
while( my $line = <$fh> ) {
last if $. > 200;
push #array, $line;
}
close($fh);
open $fh, '>', $filename or die "Can't open > $filename: $!";
print $fh #array;
close($fh);

Answer 3

There is no need to keep your own counter, perl has a special variable $. which keeps track of the input line number. You can simplify your loop like so:
while( chomp( my $line = <$fh> ) ) {
last if $. > 200;
print $fh1 "$line\n";
}
perldoc perlvar - Search for INPUT_LINE_NUMBER.

Answer 4

To write back to the original file: input.txt without using redirection:
perl -pi.tmp -we "last if $.>200;" input.txt
where
-i : opens a temp file and automatically replaces the file to be
edited with the temporary file after processing (the '.tmp'
is the suffix to use for the temp file during processing)
-w : command line flag to 'use warnings'
-p : magic; basically equivalent to coding:
LINE: while (defined $_ = <ARGV>)) {
"your code here"
}
-e : perl code follows this flag (enclosed in double quotes for MSWin32 aficiandos)