BUG: Unescaped left brace in regex is illegal here in regex; marked by <-- HERE in m/^(http|https)://%{ <-- HERE HTTP_HOST}(/.*)$/ at /usr/share/webmin/virtual-server/list_redirects.cgi line 20

Virtualmin
5

Edit line 20 in /usr/libexec/webmin/virtual-server/list_redirects.cgi to

 $dest =~ /^(http|https):\/\/%\{HTTP_HOST\}(\/.*)$/) {

Two extra backslashes inserted.
{HTTP_HOST} edited to \{HTTP_HOST\}