Perl perlsyn

"Another useful shortcut is that, if you use a literal array or hash as the argument to given , it is turned into a reference. So given(@foo) is the same as given(\@foo) , for example."

Therefore, just use an array reference like already suggested by toolic:

 when ([qw(jpeg jpg png)]) {
[download]

Or use a regex

 when (/^(?:jpeg|jpg|png)$/) {
[download]