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>perl -le"@a = qw( a b c d ); @b = grep { push(@a,'!') if !$i++; 1 } @ +a; print @b" abcd
>perl -le"@a = qw( a b c d ); for (@a) { push(@a,'!') if !$i++; push @ +b, $_ } print @b" abcd!