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    <p>There are two assignment operators: list assignment and scalar assignment. The choice is determined based on the LHS of the "<code>=</code>". (The two operators are covered in detail in <a href="http://www.perlmonks.org/?node_id=790129" rel="nofollow">here</a>.)</p> <hr> <p>In this case, a list assignment operator is used. The list assignment operator evaluates both of its operands in list context.</p> <p>So what does <code>$_=~ /^&gt;(.*)/</code> do in list context? Quote <a href="http://perldoc.perl.org/perlop.html" rel="nofollow">perlop</a>:</p> <blockquote>If the <code>/g</code> option is not used, <code>m//</code> in list context returns a list consisting of the subexpressions matched by the parentheses in the pattern, i.e., (<code>$1</code>, <code>$2</code>, <code>$3</code>...) [...] When there are no parentheses in the pattern, the return value is the list <code>(1)</code> for success. With or without parentheses, an empty list is returned upon failure.</blockquote> <p>In other words,</p> <pre><code>my ($match) = $_ =~ /^&gt;(.*)/; </code></pre> <p>is equivalent to</p> <pre><code>my $match; if ($_ =~ /^&gt;(.*)/) { $match = $1; } else { $match = undef; } </code></pre> <hr> <p>Were the parens omitted (<code>my $tmp = ...;</code>), a scalar assignment would be used instead. The scalar assignment operator evaluates both of its operands in scalar context.</p> <p>So what does <code>$_=~ /^&gt;(.*)/</code> do in scalar context? Quote <a href="http://perldoc.perl.org/perlop.html" rel="nofollow">perlop</a>:</p> <blockquote>returns true if it succeeds, false if it fails.</blockquote> <p>In other words,</p> <pre><code>my $matched = $_ =~ /^&gt;(.*)/; </code></pre> <p>is equivalent to</p> <pre><code>my $matched; if ($_ =~ /^&gt;(.*)/) { $matched = 1; # !!1 if you want to be picky. } else { $matched = 0; # !!0 if you want to be picky. } </code></pre>
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