"for" over an array is optimized; this works just as well from a memory perspective: 
for my $a_val (@a) {
    (my $s = $a_val) =~ s/x//g;
    push @b, $s if $s;
}

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In reply to Re^2: Basic list manipulation, and a bit of map() confusion... by ysth
in thread Basic list manipulation, and a bit of map() confusion... by cmv

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