$find is taken care of automatically, but you need to evaluate $replace, twice: $string =~ s/$find/$replace/gee; The first time gives you $1, and the second evaluates that to become the first parenthetical match. Example:

#!/usr/bin/perl -w

use strict;

my $string = "abcabcabc";
my $find = "a(bc)";
my $replace = '$1';

$string =~ s/$find/$replace/eeg;
print ">>$string<<\n";
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Note that $replace is defined via single quotes. That's to avoid interpolation in the assignment -- otherwise, there's an undefined value error.