as long as sub first is defined below the BEGIN block,
even if the only argument is '--first' (i.e. no invalid options),
you'll have

Undefined subroutine &main::first called at .../Getopt/Long.pm line 60
+7.
Available options are:
        --first
        --help
Invalid options passed to ....pl
BEGIN failed--compilation aborted at ....pl line 17.
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which means, as Corion already mentioned, you have to move the BEGIN block below the subroutines, which defeats the purpose.

besides, from an esthetic viewpoint, it isn't nice, if a program reacts with a "compilation error" to a wrong invocation.

I think I like haukex's variant "push @actions" best, and it would even allow for an optional --ignore-unknown-switches or --please-dont-die switch to suppress dying on invalid options ;-)