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";
}

##</code><code>##

if ("hsbn" =~ /^$action/) {
  # $action is "h", "hs", "hsb", or "hsbn"
}

##</code><code>##

my $valid = join "\n", qw( hsbn admin help quit ... );
chomp(my $action = <STDIN>);
my @matches = $valid =~ /^($action.*)/mg;

if (@matches == 0) {
  print "No command matched '$action'\n";
}
elsif (@matches > 1) {
  print "Multiple commands matched '$action': [@matches]\n";
}
else {
  print "You selected $matches[0].\n";
}