@a = ("1", "2", "3"), "4", ("5", "6"), (), "7";

##</code><code>##

@a = qw(1 2 3 4 5 6 7)

##</code><code>##

perl -e '@foos = map { /[13579]/ ? "foo" : "" } (0..50); print join "\n", @foos; print "\n\n"'

##</code><code>##

perl -e '@foos = grep { /[13579]/ ? "foo" : "" } (0..50); print join "\n", @foos; print "\n\n"'

##</code><code>##

perl -e '@foos = map { /[13579]/ ? ("foo",$_) : () } (0..50); print join "\n", @foos; print "\n\n"'

##</code><code>##

perl -e '@foos = grep { $_= (/[13579]/ ? "foo" : "") } (0..50); print join "\n", @foos; print "\n\n"'