Adding the commas indeed work. However, there's another, more general possibility too: factor the loop body out to a function and use three different foreach loops. Like, instead of

for (@array1, @array2, @array3) {
    print "met $_";
}
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you can write

my $body = sub {
    print "met $_";
}
for (@array1) { &$body() }
for (@array2) { &$body() }
for (@array3) { &$body() }
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This works even if you have a more complicated iterator than foreach.