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POWhat is the difference in Perl when passing a variable in a regular expression between using $variable and ${variable}
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  1. POWhat is the difference in Perl when passing a variable in a regular expression between using $variable and ${variable}
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    copied!<p>I am reviewing some ClearCase triggers written in Perl. I have noticed that in some regular expressions, variables are passed either straighforwardly or with their names in curly brackets.</p> <p>For example, I have the following line of code in a trigger:</p> <pre><code>if ($baseline !~ /^${component}_(|.*_)$phase\.\d+(|[a-z]|-\d+|${automateddigit})$/ &amp;&amp; $baseline !~ /^${project_root}_$phase\.\d+(|[a-z]|-\d+|${automateddigit})$/) </code></pre> <p><code>$component</code>, <code>$phase</code>, <code>$automateddigit</code>, <code>$project_root</code> are all variables.</p> <p>Why are some passed as <code>$variable</code> and other passed as <code>${variable}</code> in the regular expression?</p> <p>Does it come from how they are initialised?</p> <p>Here are the line of code initialising them:</p> <pre><code>($project = $ENV{CLEARCASE_PROJECT}) =~ s/\@.*$//; ($component = $ENV{CLEARCASE_COMPONENT}) =~ s/\@.*$//; ($project_root, $phase) = ($project =~ /^(.*)_(R\d+.*)$/); exit(0) if (! $phase); $phase .= ".0" if ($phase =~ /^R\d+$/); $automateddigit = ''; $istream = `cleartool desc -fmt "%[istream]p" project:$ENV{CLEARCASE_PROJECT}`; $componentlist = `cleartool desc -fmt "%[components]Cp" stream:$ENV{CLEARCASE_STREAM}`; $componentsnbr = split(',', $componentlist); if ($componentsnbr &gt; 1) { $automateddigit .= '\\.\\d+'; } </code></pre>
 

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