using floats to compute modulo does not seem reasonable to me.

I only included this:

my $n = 534587;
print "even\n" if($n % 2 == 0);    # modulo operator of possibly a flo
+at or possibly an integer (*)
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because

1. it is equivalent to the OP's "Most obvious (easiest) solution" (infact code-ninja used this exact example here: Re^2: A mod2 Machine.)
2. it might actually be doing a (possibly comparatively slow) float operation because use integer was not used.
   It probably had to go: float 534587 --> integer 534587 --> integer modulo operation on integer 534587

Whereas doing a proper integer bit test should be faster:

use integer;
my $n = 534587;
print "even\n" if($n & 1 == 0);    # checking LSB with Bitwise And on 
+an integer
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