Perl 6 way of Factorial function.

fac.pl6.txt

#!/usr/bin/perl6

use v6;

# overloading string 'x' operator
multi infix:<x> (Int \a, Int \b) { a * b }

# but we still want the string 'x' operator
multi infix:<x> (Str \a, Int \b where * > 1) { [~] gather for ^b { take a } }

multi postfix:<!> (1) { 1 }
multi postfix:<!> (Int \n where * > 1) { n x (n - 1)! }

say 5!; # 120

# end of script