You can eval it: 
  % cat x.pl  
  $_ = 'foo';          
  $lhs = '(.)oo';      
  $rhs = '\1ar';       
  eval "s/$lhs/$rhs/"; 
  print "$_\n";        
  % perl x.pl 
  far                  
  %

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In reply to RE: How can I combine backreferences and regex interpolation? by knight
in thread How can I combine backreferences and regex interpolation? by Anonymous Monk

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