It does one thing nashdj alluded to. As the last statement in a block, the resultant value of the block is the value in the variable.

For example, in the Everything source they'll occasionally have a subroutine that does something like:

sub do_thisorthat {
    my ($text, $op) = shift;
    my $code = get_op($op);
    $code->$text;

    # manipulate text
    $text;
}
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