http://www.perlmonks.org?node_id=176873


in reply to factorialmath.

Since this clearly isn't homework (cough), here's an idea of how to solve the problem: 
#!/usr/bin/perl

package F;sub TIESCALAR{bless[],pop}
sub FETCH{$v=$n=pop()->[$|];$v*=--$n
while(1<$n);$v}sub STORE{shift()->[0
]=pop}tie($f,F);$f=pop;print$f,$/,$@

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