The first while calls the match in list context, you get all matches but grab only the first line.

Since the string is exhausted the loop starts from the beginning and the match is never empty.

while normally imposes scalar context but you broke the logic.

update

just try grabbing more vars to understand what is happening

  DB<118> while (my ($line1,$line2) = $data =~ m/^(.*)$/gm) { print "$
+line1 $line2\n"; last if $x++>5 }
some random
some random
some random
some random
some random
some random
some random
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