The syntax you're using to access the array reference in the hash is incorrect. It should be

@{$spr_hash{$file_name}}
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The extra braces are important. Otherwise what you've got is a single-element slice of the hash referenced by the scalar $spr_hash. Enabling use strict would have given you a hint that something was wrong by pointing out that you were referencing this undeclared scalar variable. Truthfully, though, you can write those two lines more simply as

$spr_hash{$file_name} = [<FH>];
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and put the file contents right in the anonymous array. No need to initialize it with a blank array first.