What is the use of ${1} in the below statement instead of $1?

 $text =~ s/(<jrnl\;\d+\;)[^>]*(>)/${1}${annualIssue}\;${first}\\N${last}${2}/gs;

Thank you

In reply to what is the use of derefernce in substitution? by tej

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
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