Using a heredoc would have the same effect with less magic, although the code layout would be different.

print "now in runtime...\n";

BEGIN {
    open my $fh , '<', \<<'__EOI__' or die;
foo
bar
quux
now in runtime...
now in main
__EOI__

    while (<$fh>) { 
        print "DATA: $_";
    }
}

...
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