I am taking baby steps to understanding out to read in, modify file(s) and then send modified file to output. Here is my attempt to just read in a file and send it to output. 
#!/bin/perl
use v5.12;
use warnings;

       my $in = $ARGV[0];
       if (! defined $in) {
          die "Usage: $0 filename";
       }


       my $out = $in;
       $out =~ s/(\.\w+)?$/out/;

       if (! open $in_fh, '<', $in ) {
          die "Can't open '$in': $!";
          }

       if (! open $out_fh, '>', $out) {
          die "Can't write '$out': $!";
          }

[download]

Here is the errors that I received: 

Global symbol "$in_fh" requires explicit package name at ./exer_9_2 li
+ne 14.
Global symbol "$out_fh" requires explicit package name at ./exer_9_2 l
+ine 1

[download]

What 'package' am I missing?

Catfish

In reply to First attempt at bringing in file for input/output by catfish1116

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