$ perl -Mstrict -Mwarnings -E '
    use Getopt::Long;
    sub sub1 { state $i = 0; ++$i; say "$i: >>>$_<<<" for @_ }
    GetOptions( "test=s{3}" => \&sub1 );
' -- --test a b c
1: >>>test<<<
1: >>>a<<<
2: >>>test<<<
2: >>>b<<<
3: >>>test<<<
3: >>>c<<<