How about this?

#assuming:
#use strict;
#$q is initialized
#sub inerror is defined

my @edittypes = qw(.htm .html .txt);
my $regex = join "|", map {'\Q' . $_ . '\E'} @edittypes;
my $file = $q->param('select');
unless $file =~ /(?:$regex)$/  &inerror("You can only edit @edittypes"
+);
[download]

--

flounder