Hi,
Your first code snippet contains

my $node;
if ($node eq...
[download]

Is this a typo? $node will always eq undef in this case. Did you mean

my $node = param('node')
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You could do it something like this: (untested code):

#!/usr/bin/perl
use CGI;

my $node = param('node');

my %lookup_table = (how => 'how_sub', foo => 'foo_sub');
if ($lookup_table{$node} ne '') {
    &{$lookup_table{$node}};
} else {
    print "Unknown sub called\n";
}

sub how_sub {}
sub foo_sub {}
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The %lookup_table and if routine makes sure users cant choose any old sub to run,
just the ones you define in the lookup_table.

Smitz