You can still use that method if you like, as by shifting $arg from @ARGV you remove it from the list of files that will be processed by <>. And you could still use the -two syntax if you liked, here's an example:

use strict;
use warnings;

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

sub usage {
  print "Usage: $0 [-command]\n";
  print "Available commands:\n";
  print " -$_\n" for sort keys %dispatch;
  exit 1;
}

my $arg = shift @ARGV;

usage() unless defined $arg;
usage() unless $arg =~ /^-/;
$arg =~ s/^-//;
usage() unless exists $dispatch{$arg};


$dispatch{$arg}->();


sub sub1 {
    print "one: $_" for <>;
}

sub sub2{
    print "two: $_" for <>;
}
sub sub3 {
    print "three: $_" for <>;
}
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