... I'm not sure how the "{([0-6BS])}" will get interpreted as. "{" and "}" in a regex are normally used to quantify the number of matches.

Apparently, if the RE compiler can't see anything in the regex that looks like a count or count range, it just gives up on the whole counted quantifier thing and takes the curlies as literal characters.

c:\@Work\Perl>perl -wMstrict -le
"$_ = 'xxqr{S}xx';
 print qq{matched '$&', \$1 is '$1'} if m/qr{([0-6BS])}/;
"
matched 'qr{S}', $1 is 'S'
[download]

(Tested under ActiveState 5.8.9, Strawberry 5.14.4.1.)

To store a regex as a hash key, you could prefix the regex with a character that won't otherwise appear as the first character of any of your has keys.

I still prefer some sort of separate tag to distinguish pattern from exact matching:

c:\@Work\Perl>perl -wMstrict -MData::Dump -le
"my %options = (
   qr{ x (Y) z }xms => { type => 'pattern',  name => 'foo', },
   '(?x) x (Y) z '  => { type => 'pattern',  name => 'fum', },
   'xYzzy'          => { type => 'exact',    name => 'bar', },
   'zzzzz'          => { type => '?????',    name => 'zot', },
   );
 dd \%options;
 ;;
 $_ = 'xYzzy';
 for my $p (sort keys %options) {
   my ($p_type, $p_name) = @{ $options{$p} }{ qw(type name) };
   if ($p_type eq 'pattern') {
     if ($_ =~ $p) { print qq{'$p_name' pattern match of $p, \$1 is '$
+1'}; }
     }
   elsif ($p_type eq 'exact') {
     if ($_ eq $p) { print qq{'$p_name' exact match of '$p'}; }
     }
   else {
     die qq{unknown: $p; type '$p_type'; name '$p_name'};
     }
   }
"
{
  "(?^msx: x (Y) z )" => { name => "foo", type => "pattern" },
  "(?x) x (Y) z " => { name => "fum", type => "pattern" },
  "xYzzy" => { name => "bar", type => "exact" },
  "zzzzz" => { name => "zot", type => "?????" },
}

'foo' pattern match of (?^msx: x (Y) z ), $1 is 'Y'
'fum' pattern match of (?x) x (Y) z , $1 is 'Y'
'bar' exact match of 'xYzzy'
unknown: zzzzz; type '?????'; name 'zot' at -e line 1.
[download]

(Test under same Perl versions as above.)