[MacPerl] replace numbers

[Allan Juul]

hi
might be silly question
how do you actually replace numbers when immidialtely following a  $1, $2 or
so?

like this will return stuff23 :

$a = 23;
$_ =~ s/some (stuff)/$1$a/g

i had hoped something in the vein of this would have done it:

$_ =~ s/some (stuff)/$1\23/g

thanks 

allan