You can use a hashtable lookup of closures (aka: code refs)

This would let you build up the hashtable in any order you want, possibly adding to it in multiple files (maintained by different people), possibly refering to methods / coderefs written by other people, in other packages.

Understanding how the example below works is left as an excersize fo the reader.
(hint: look at perldoc perlref)

#!/usr/local/bin/perl -wl
use strict;

my $function = $ARGV[0];
my $input_file = $ARGV[1];;

sub create_file {
    my $file = shift;
    open (NETH, ">$file");
    #actions
    print "Creating $file";
    close (NETH);
}

my %function_registry =
    (
     'open' => sub {
         my $file = shift;
         open (BLAH, "$file");
         #actions
         print "Opening $file";
         close (BLAH);
     },
     'create' => \&create_file
     );
&{$function_registry{$function}}($input_file);

__END__
[hossman@laptop ~]$ monk.pl create /tmp/file
Creating /tmp/file
[hossman@laptop ~]$ monk.pl open /tmp/file
Opening /tmp/file
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