Webmin php-lib.pl modification
First of all you should use single quotes instead of double quotes for a simpler syntax:
...push(@phplines, '<FilesMatch \.php$>');push(@phplines, 'SetHandler fcgid-script');push(@phplines, '</FilesMatch>');...
Check this specific file for syntax errors with
perl -c /usr/share/webmin/virtual-server/php-lib.pl
Add a log file somewhere in this file so you are sure this file gets called at all. E.g. add something like this before the code shown above:
my $fh;open($fh, '>>', "/tmp/test.log") or die "Couldn't open: $!";print $fh "This file is actually used!";close $fh;...