exists $cells->{$p->[0],$p->[1]} or die;

##</code><code>##

exists $cells->{ join ':', @{$p} } or die;

##</code><code>##

Str:   7 wallclock secs ( 6.58 usr + 0.00 sys =.58 CPU) @ 30404.38/s (n=200000)
Multi: 8 wallclock secs ( 7.98 usr + 0.00 sys =.98 CPU) @ 25050.10/s (n=200000)

##</code><code>##

exists $cells->{ join ':', $p->[0], $p->[1] } or die;