my $re = qr/a/;

say "a" =~ /$re/    || 0;   # 1
say "A" =~ /$re/    || 0;   # 0
say "a" =~ /$re/i   || 0;   # 1
say "A" =~ /$re/i   || 0;   # 0

my $pat1 = "(?^:a)";

say "a" =~ /$pat1/  || 0;   # 1
say "A" =~ /$pat1/  || 0;   # 0
say "a" =~ /$pat1/i || 0;   # 1
say "A" =~ /$pat1/i || 0;   # 0

my $pat2 = "a";

say "a" =~ /$pat2/  || 0;   # 1
say "A" =~ /$pat2/  || 0;   # 0
say "a" =~ /$pat2/i || 0;   # 1
say "A" =~ /$pat2/i || 0;   # 1  XXX

##</code><code>##

my ( $pat, $flags ) = re::regexp_pattern( $re );

##</code><code>##

my $re = eval "no re; qr/\$pat/$flags";