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use strict;
use warnings;
...

    return @ends;
}

sub find_ends {
    local $_ = $_[0];
...

    return @ends;
}

Benchmark: running rd, tb for at least 10 CPU seconds...
        rd:  9 wallclock secs (10.36 usr +  0.01 sys = 10.37 CPU) @ 29
+908.68/s (n=310153)
...
      Rate   tb   rd
tb  5603/s   -- -81%
rd 29909/s 434%   --