Drawing on dvergin's idea, what about this? 
sub safeswitch {
        my @P = (undef,$1,$2,$3,$4,$5,$6,$7,$8,$9);
        $_[0] =~ s/\$(\d)/$P[$1]/g;
        $_[0];
}

my $str = "abcdefghijafjafjkagjakg";

my $pat = '(a.)';
my $repl = '$1 ';

$str =~ s/$pat/safeswitch($repl)/eg;

print $str,$/;

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The advantage here is that you don't end up re-evaluating the function code each time, just the function call.

In reply to Re: $1 in variable regex replacement string by tadman
in thread $1 in variable regex replacement string by dvergin

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