Hello fionbarr,

When I use 'given/when' I get the message 'given is experimental' and the program will not compile.

Are you using a very old version of Perl? According to perlexperiment, the smartmatch feature was introduced in Perl 5.10.0, so unless your version is older than that, the program should compile OK — but emit warnings — as long as you remember to use feature 'switch':

 0:33 >perl -we "use feature 'switch'; my $c = 42; given ($c) { when (
+$_ < 50) { print 'Yes!' } }"
given is experimental at -e line 1.
when is experimental at -e line 1.
Yes!
 0:33 >
[download]

The warnings can be turned off with this pragma:

no warnings 'experimental::smartmatch';
[download]

But if you’re going to use when, you should still replace the topicaliser given with its more prosaic alternative for, as explained by brian_d_foy in his article “Use for() instead of given().”

However, even the use of when is not recommended for production code. For other switch options, begin with How-do-I-create-a-switch-or-case-statement of perlfaq7. And if a dispatch table doesn’t meet your particular needs, what’s wrong with if/elsif/.../else, anyway? :-)

Hope that helps,