my %sub_named
    = ( this => \&this,
        that => \&that,
      );
my $ref = 'this';
my $x;
if ( exists $sub_named{ $ref } ) {
    $x = $sub_named{ $ref }->();
}
else {
    # error, no sub named $ref
}

##</code><code>##

my @sub_list = qw( this that );
my %sub_named = map { $_ => eval "\\&$_" } @sub_list;
# etc.

##</code><code>##

use English '-no_match_vars';

my $ref = 'this';
my $x = eval "&$ref()";
if ( my $error_message = $EVAL_ERROR ) {
    if ( $error_message =~ /^Undefined subroutine / ) {
        # a dispatch table would have caught this
    }
}