readline() on unopened filehandle

[invaderzard]

#!/usr/bin/perl
use Modern::Perl;
use File::Slurp qw/read_file write_file/;
my $pfaminput ='D://ARP//Downloads//Trembl//toxinpospf.txt';
my $seedinput ='D://ARP//Downloads//PFACFULL.txt';
#open OUTPUT, ">", 'D://ARP//Downloads//trembl//Toxin-NegativeACClist.
+txt';
#select OUTPUT;

while (<$pfaminput>){
    my $pfam = $_;
    print $pfam;
#while (<$seedinput>)    {
#    my $blah = substr $_, 0, 5;
#    if ($blah=<$pfaminput>) {
#print $_;        
#    }
#    
#}
}

Hi all. When I execute this code, I get: readline() on unopened filehandle at <insertprogramnamehere> line 9

This is my line 9

while (<$pfaminput>){

Why is this? Please help and many thanks!

[Corion]

So, Perl tells you that the filehandle is not opened.

Where did you open the filehandle to your file?

See open or maybe use File::Slurp?

[NetWallah]

Since you are just a few months into perl, here is the canonical way to do this (Note - I changed the name and meaning of your variable for clarity):

my $pfaminput_filename ='D:/ARP/Downloads/Trembl/toxinpospf.txt'; 
       # Double fwd-slash is not necessary

open (my $pfaminput_filehandle , "<" , $pfaminput_filename ) 
         or die "Can't open '$pfaminput_filename' : Error is : $!";

while (my $pfam = <$pfaminput_filehandle>){
   print $pfam;
}

close $pfaminput_filehandle;

Update: Corrected variable name inside error message.

[aitap]

$pfaminput is just a scalar containing file path, not a filehandle. You need to open a filehandle in order to read from it.