Perl's parser uses heuristics to make the distinction between hashes and code-blocks.

Because of the numbers (remember => is just a fat comma) this is interpreted as a hash.

eliminating the ; helps seeing what's happening

> perl -MO=Deparse
{
  7, 10
}
__END__
+{7, 10};           # <-- a literal hash
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But what do you expect a codeblock with 7,10 to do?

EDIT:

one workaround to help the parser understand your intentions is an early semicolon

 perl -MO=Deparse
{
  ; 7,10;
}
__END__
{
    '???', '???';    # <-- constants in a codeblock
}
[download]