A few more examples would help. I'm only inserting the newline to make it easy to see where I adding the spaces.

#! perl -slw
use strict;
use Inline::Files;

select OUTPUT;

while( <DATA> ) {
    s[(.{9,18})(?=\b\W)][$1 \n]g;
    print;
}

__DATA__
for(1..20){$bar=$bop[1];print"$bar/$baz,$foo[$baz]"}
for(1..20)%7B%24bar%3D%24bop%5B1%5D%3Bprint%22%24bar%2F%20%24baz%2C%24
+foo%5B%24baz%5D%22%7D
__OUTPUT__
for(1..20){$bar 
=$bop[1];print 
"$bar/$baz,$foo 
[$baz]"}
for(1..20)%7B 
%24bar%3D%24bop 
%5B1%5D%3Bprint%22 
%24bar%2F%20%24baz 
%2C%24foo%5B%24baz 
%5D%22%7D
[download]