$ perl -e 'my $s="-]"; print "a\n" if $s =~ /[___]]/'
$ perl -e 'my $s="-]"; print "a\n" if $s =~ /[]___]/'
a
$ perl -e 'my $s="-]"; print "a\n" if $s =~ /[___-]/'
a
$ perl -e 'my $s="-]"; print "a\n" if $s =~ /[-___]/'
a