[Perl] Regexp help

[nothingmuch]

i have a regexp for a turing machine utility:

$sooey =~ s/([01_\@\#\$\%\&a-zA-Z])/$i,_,++$i,$1,>\n/g;

i want ++$i to actually *BE* ++$i (i mean $i increased by one, and 
returned)

i'm not a regexp expert, so how do you do this?