readline() on closed file-handle is coming when reading the file

[ulaksh]

readline() on closed filehandle is coming when executing the perl script. I am trying to get the number of line in file which contain the X. I am not getting where is the issue.

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


my ($filename, $lines_num, $line, $c);

$lines_num = 0;
$filename = "input.txt";
open my $in,  "<", $filename;
while ($line = <$in>)
{
    $c = substr($line, 0, 1);
    if (lc($c) eq "x")
    {
        $lines_num++;
    }
}
close($in);

print "In " , $filename, " there are ",
    $lines_num, " lines that start with \"X\".\n";

my input file contains as below
X
XX
XXX
XXXX
XXXXX
XXXXXX
XXXXXXX
XXXXXXXX
XXXXXXXXX
XXXXXXXXXX
XXXXXXXXXXX
XXXXXXXXXXXX
XXXXXXXXXXXXX
XXXXXXXXXXXXXX
XXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXX

And my output show "readline() on closed filehandle $in at filehandleoperator.pl line 12."

[philiprbrenan]

Please add:

  or die "Cannot open file";

after the open.

[johngg]

Or, even better:

  or die "Cannot open file: $!";

so that you can see the o/s error generated when the filehandle failed to open.

[2teez]

OR,
add use autodie qw(open close); just after use warnings; in your script.
Your script should work fine, except you have other things in mind.
For detailed information check autodie

Cheers