perl -e '@array = qw (hello world 1 2 3); @req = qw (2 3 4); $str = print join (",",@array[@req]), $/;'
__END__
1,2,3


##</code><code>##

perl -e '@wperiod = qw (hi.1 hi.2 hi.3); print join (",", map {s/\.//g; $_} @wperiod), $/;'
__END__
hi1,hi2,hi3