my $t = 0;
my @x = grep $t^=1, split /(?<=(.))(?!\1)/, $x;
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my @x;
push(@x, $1) while $x =~ /((.)\2*)/g;
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my $t = 0;
my @x = grep $t^=1, $x =~ /((.)\2*)/g;
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my $t = 0;
my @x = grep $t^=1, map /((.)\2*)/g, $x;
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$t is for "toggle". grep is used to filter out every second item.