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for my $bn ( @B_CHECKS ) {
   my $re = qr/^(?:0|5|6)0+\Q$bn\E$/;
...
      }
   }
}

my ($re) = map qr/^(?:0|5|6)0+($_)$/,
           join '|',
...
      print "$1 = $cn\n";
   }
}

use Regexp::List qw( ) 

...
      print "$1 = $cn\n";
   }
}

my %B_CHECKS = map +($_ => 1), @B_CHECKS;
for my $cn ( @CS_CHECKS ) {
...
      print "$bn = $cn\n";
   }
}