use Text::Abbrev;
use strict;

print "Enter a command: ";
chomp(my $action = <STDIN>);  # they could enter 'adm' or 'h'
my %modes = abbrev(qw( hsbn admin ... ));

# if $modes{$action} is defined, that means it is a
# NON-AMBIGUOUS abbreviation of 'hsbn', 'admin', etc.
if (defined(my $fullaction = $modes{$action})) {
  if ($fullaction eq 'hsbn') { ... }
  elsif ($fullaction eq 'admin') { ... }
  ...
}
else {
  print "$action was ambiguous.\n";
}