I'd go with a lookup-table. Since you can look up directly in a hash table, a list will have to do...

my @keys = (
 [ "key1" => sub { handle_key1 } ], # inline anony sub
 [ "key2" => \&handle_key2       ], # use a named function
 [ "key3" => sub { ... }         ],
 # ...
);

use List::Util qw(first);

# find the entry
my $data = first { index($mystring, $_->[0]) >= 0 } @keys;

# call the code
$data->[1]->();
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