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copied!<p>Below are a few tips to make your code more idiomatic:</p> <ul> <li>The <a href="http://perldoc.perl.org/perlvar.html#%24INPUT_LINE_NUMBER" rel="nofollow noreferrer">special variable <code>$.</code></a> already holds the current line number, so you can likely get rid of <code>$lctr</code>.</li> <li>Are empty lines really errors, or can you ignore them?</li> <li>Pull apart the list returned from <code>split</code> and give the pieces names.</li> <li>Let Perl do the opening with the <a href="http://perldoc.perl.org/perlop.html#I/O-Operators" rel="nofollow noreferrer">"diamond operator"</a>:</li> </ul> <blockquote> <p>The null filehandle <code><></code> is special: it can be used to emulate the behavior of <code>sed</code> and <code>awk</code>. Input from <code><></code> comes either from standard input, or from each file listed on the command line. Here's how it works: the first time <code><></code> is evaluated, the <code>@ARGV</code> array is checked, and if it is empty, <code>$ARGV[0]</code> is set to <code>"-"</code>, which when opened gives you standard input. The <code>@ARGV</code> array is then processed as a list of filenames. The loop</p> <pre><code>while (<>) { ... # code for each line } </code></pre> <p>is equivalent to the following Perl-like pseudo code:</p> <pre><code>unshift(@ARGV, '-') unless @ARGV; while ($ARGV = shift) { open(ARGV, $ARGV); while (<ARGV>) { ... # code for each line } } </code></pre> <p>except that it isn't so cumbersome to say, and will actually work.</p> </blockquote> <p>Say your input is in a file named <code>input</code> and contains</p> <pre>Campbell's soup,0.50 Mac & Cheese,0.25</pre> <p>Then with</p> <pre><code>#! /usr/bin/perl use warnings; use strict; die "Usage: $0 coupon-file\n" unless @ARGV == 1; while (<>) { chomp; my($product,$discount) = split /,/; next unless defined $product && defined $discount; print "$product => $discount\n"; } </code></pre> <p>that we run as below on Unix:</p> <pre>$ ./coupons input Campbell's soup => 0.50 Mac & Cheese => 0.25</pre>

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