You want a hash of arrays. That simplifies the logic and puts the data all in one place.

my %data = (
    foo1 => [
        '1 - 201 - 229',
        '2 - 201 - 229',
        '3 - 201 - 229',
    ],

    foo2 => [
        '1 - 201 - 218',
        '2 - 201 - 218',
        '3 - 201 - 218',
        '4 - 201 - 218',
        '5 - 201 - 218',
        '6 - 201 - 218',
        '7 - 201 - 218',
   ],

# . . . 
);
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Then you can just say,

my @act_bsites = @{$data{$dataset}};
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If the 1-150 ordering is natural and important, you may want to drop the 'foo' part of the designation and use an array instead of a hash.

Update: I don't understand how hardcoding the data in an extended if-else construct improves anything with respect to hard-won data. Here's a version with a seperate data file:

# file: /path/to/foosites
{
    foo1 => [
        '1 - 201 - 229',
        '2 - 201 - 229',
        '3 - 201 - 229',
    ],

    foo2 => [
        '1 - 201 - 218',
        '2 - 201 - 218',
        '3 - 201 - 218',
        '4 - 201 - 218',
        '5 - 201 - 218',
        '6 - 201 - 218',
        '7 - 201 - 218',
   ],

# . . . 
};
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and then in your code it can be as simple as,

my @act_bsites = @{(do '/path/to/foosites')->{$dataset}};
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