Consider this function: 
sub foo {
  my ($text, $to) = @_;
  $text =~ s{(\d+)}{$to};
  $text;
}

print foo("123", 'capture 1 is $1');

[download]
I'd like it to print 'capture 1 is 123', but it prints 'capture 1 is $1'. It's treating $to as a string literal and ignoring the occurrence of $1 in the string.

I have since figured out this: 

sub bar {
  my ($text, $to) = @_;
  $text =~ s{(\d+)}{qq{qq{$to}}}ee;
  $text;
}

print bar("456", 'capture 1 is $1'); # prints capture 1 is 456

[download]

Is there any other way to get $1, $2, etc. interpolated without resorting to using the /ee modifier?

In reply to Interpolate $1 in: s{...}{$to} by perl5ever

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