Hi everyone. I have a question with regards to a Perl program that I have written for Exercise 2.1 of the book Learn Perl the Hard Way. The question goes like:

Write a program called grep.pl that takes a pattern and a list of files as command line arguments, and that traverses each file printing lines that match the pattern.

I have 4 files of which their contents are listed below: file_list.txt --> contains a list of files: "a.txt", "b.txt", "c.txt" a.txt --> Contains the word "I" b.txt --> Contains the words "am going to" c.txt --> Contains the word "school"

I have tried to write the program below, but I don't understand why it only prints the contents from a.txt, i.e. it only prints the word "I". I inserted print functions along the way and I realized that the subroutine "open_file" is called only once but I don't understand why this happens.

May I ask if anyone can give a hint on resolving this?

Thank you! 

#!/usr/bin/perl

use strict;
use warnings;

sub open_file {
    my $file = scalar(@_);
    foreach my $temp (@_) {
        open FILE, $temp;
        while (my $line = <FILE>) {
            print $line;
        }
    }
}

sub grep_file {
    my $file = shift;
    open FILE, $file;
    while (my $line = <FILE>) {
        open_file ($line);
    }
}

grep_file @ARGV

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In reply to Question on File Handler and Subroutines in Perl by Anonymous Monk

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