$in=param('in');
if($in eq "this"){&this}
if($in eq "that"){&that}
if($in eq "foo"){&foo}
if($in eq "bar"){&bar}
if($in eq "zzz"){&zzz}
# imagine a lot more

##</code><code>##

$in=param('in');
@actions=qw(this that foo bar zzz); # names of subroutines and input values
foreach $_(@actions){ if($in eq $_){&$_()}}