How about:

sub template {
    my $e = shift;

    my $not_common_a = 
        $e eq 'b' ? sub { ... } :
        $e eq 'u' ? sub { ... } :
                    sub { ... } ;

    my $not_common_b = 
        $e eq 'x' ? sub { ... } :
                    sub { ... } ;

    return sub {
        $common_stuff;
        $not_common_a->();
        $more_common_stuff;
        $not_common_b->();
    }
}
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Makeshifts last the longest.