Jeri has asked for the wisdom of the Perl Monks concerning the following question:

I get the error "readline() on closed filehandle $INFILE at Fileappendor.pl line 20."

This is a simple example of my problem. I can't seem to figure it out. Even if I don't ever close the filehandle, I still get the error. I feel like this is a conceptual newbie mistake. Can someone please address what I'm doing wrong? Thanks in advance. 

#!usr/bin/perl5.8.8

use strict;
use warnings;

fileappendor();

sub fileappendor
{
my $fileno = 1;
my $outfile = "proteintable";

open (my $OUTFILE,">", $outfile);

while($fileno <= 152)
{
my $infile = $fileno."_FamDATA";
open (my $INFILE,"<", $infile);

    while(<$INFILE>)
    {
    print $OUTFILE $_;
    }

close ($INFILE);
$fileno++;
}
} #end of sub fileappendor

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Re: readline() on closed filehandle
by toolic (Bishop) on Oct 07, 2011 at 21:02 UTC
    One way to get that warning message is if the open failed for your input file. Check if the open succeeded, for example, with autodie.
[reply]
Re: readline() on closed filehandle
by ww (Archbishop) on Oct 07, 2011 at 23:59 UTC

    ... as toolic said... or, another way to check:

    open (my $OUTFILE,">", $outfile) or die "Could not open $OUTFILE, $!";

    And why does that example deal with your outfile? Because, it's a 'really good idea' (©) to check all your opens and closes!

[reply]
[d/l]
      It might be better to die with the lowercase $outfile, though, or avoid such similar names for two different things.
[reply]
        ... certainly the 2nd --
        " ...avoid such similar names for two different things." (emphasis added!)

        ++ choroba.

        But I'm not sure the first really cures anything. choroba's first comment got me experimenting with code minimally modified from the OP's ...

        #!/usr/bin/perl
use strict;
use warnings;
use 5.012;
# #930268

my $OUTFILE;
my @outfile=("F:/_Perl_/pl_test/abcd.out", "dev/nul/xyz.out");

for my $outfile(@outfile) {
    # $OUTFILE is a glob; dereference using $$OUTFILE. Otherwise warni
+ng is ambiguous:'not open GLOB(0x1628c24) using'
    open ($OUTFILE,">", $outfile) or warn "\t Could not open $$OUTFILE
+ using \$outfile ($outfile), $!";
    say "\t \$outfile is now $outfile";
    print $OUTFILE "I wuz here in vers 1\n" or warn "\t Problem is wit
+h \$outfile: $outfile\n";
    close ($OUTFILE);
}

say "\n\n" . "-" x10 . " 2nd vers using lc \$outfile in the 'die'\n";

my $OUTFILE2;
my @outfile2 = ("F:/_Perl_/pl_test/abcd2.out", "dev/nul/pqrst.out");

for my $outfile2(@outfile2) {
    say "\t \$outfile2 is currently $outfile2";
    open ($OUTFILE2,">", $outfile2) or warn "\t Could not open $outfil
+e2 using \$outfile2, $!";
    print $OUTFILE2 "vers 2 produced this line\n" or warn "\t Problem 
+is with \$outfile2: $outfile2\n";
    close ($OUTFILE2);
}

        [download]

        The results don't seem to me to support a preference for which $var to 'die' (or, in my code, to 'warn'):

        F:\_Perl_\pl_test>F:\_Perl_\pl_test\930268.pl
      $outfile is now F:/_Perl_/pl_test/abcd.out
      Could not open *main::$OUTFILE using $outfile (dev/nul/xyz.out),
+ No such file or directory at F:\_Perl_\pl_test\930268.pl line 12.
      $outfile is now dev/nul/xyz.out
print() on closed filehandle $OUTFILE at F:\_Perl_\pl_test\930268.pl l
+ine 14.
      Problem is with $outfile: dev/nul/xyz.out


---------- 2nd vers using lc $outfile in the 'die'

      $outfile2 is currently F:/_Perl_/pl_test/abcd2.out
      $outfile2 is currently dev/nul/pqrst.out
      Could not open dev/nul/pqrst.out using $outfile2, No such file o
+r directory at F:\_Perl_\pl_test\930268.pl line 25.
print() on closed filehandle $OUTFILE2 at F:\_Perl_\pl_test\930268.pl 
+line 26.
      Problem is with $outfile2: dev/nul/pqrst.out


10/08/2011  09:06a                  22 abcd.out  # content as expected
+ from the code above
10/08/2011  09:06a                  27 abcd2.out # "
               2 File(s)             49 bytes

        [download]

        Those with greater wisdom may add insight with their comments (I hope).

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