use strict;
use warnings;

my %dispatch = (
  one => \&sub1,
  two => \&sub2,
  three => \&sub3,
);

my $arg = shift @ARGV;
if (defined $arg && exists $dispatch{$arg}) {
    $dispatch{$arg}->();
} else {
  print "Usage: $0 [-command]\n";
  print "Available commands:\n";
  print " -$_\n" for sort keys %dispatch;
}

sub sub1 {
print "sub one";
}

sub sub2{
print "sub two";
}

sub sub3 {
print "sub three";
}