$ perl -E 'my $re = qr{([0-6BS])}; say $re'
(?^u:([0-6BS]))

##</code><code>##

$ perl -E 'my $re = qr{([0-6BS])}; say ref($re)'
Regexp

##</code><code>##

$ perl -E 'my $re = qr{([0-6BS])}; my %x = ($re, 1); my @y = keys %x; say $y[0]'
(?^u:([0-6BS]))

##</code><code>##

$ perl -E 'my $re = qr{([0-6BS])}; my %x = ($re, 1); my @y = keys %x; say "|", ref($y[0]), "|"'
||

##</code><code>##

$ perl -E 'my $re = qr{([0-6BS])}; $_ = "B"; /$re/; say $1'
B

##</code><code>##

$ perl -E 'my $re = qr{([0-6BS])}; my %x = ($re, 1); my @y = keys %x; $_ = "B"; /$y[0]/; say $1'
B