my $Sun = 2**0;    # That's 1  or 00000001 in binary. 
my $Mon = 2**1;    # That's 2  or 00000010 in binary. 
my $Tue = 2**2;    # That's 4  or 00000100 in binary. 
my $Wed = 2**3;    # That's 8  or 00001000 in binary. 
my $Thu = 2**4;    # That's 16 or 00010000 in binary. 
my $Fri = 2**5;    # That's 32 or 00100000 in binary. 
my $Sat = 2**6;    # That's 64 or 01000000 in binary.

my $mask = 19;    # For example.  00010011 in binary. 

print "Sunday\n"   if ($mask & $Sun); # True
print "Monday\n"   if ($mask & $Mon); # True
print "Tuesday\n"  if ($mask & $Tue); 
print "Wednesay\n" if ($mask & $Wed); 
print "Thursday\n" if ($mask & $Thu); # True
print "Friday\n"   if ($mask & $Fri); 
print "Saturday\n" if ($mask & $Sat);