Revert "More simple regexp"

This reverts commit 2feb4a40aa.

Closes: #1876

lemonldap-ng-handler/lib/Lemonldap/NG/Handler/Main/Reload.pm

@@ -568,7 +568,7 @@ sub substitute {
     $expr =~ s/\$ip\b/\$ENV{REMOTE_ADDR}/sg;
 
     # substitute vars with session data, excepts special vars $_ and $\d+
-    $expr =~ s/\$(?!(?:ENV|env)\b)([_a-zA-Z]\w*)/\$s->{$1}/sg;
+    $expr =~ s/\$(?!(?:ENV|env)\b)(_\w+|[a-zA-Z]\w*)/\$s->{$1}/sg;
     $expr =~ s/\$ENV\{/\$r->{env}->\{/g;
     $expr =~ s/\$env->\{/\$r->{env}->\{/g;