$srciphash{$srcip}{$dstip} = 1;

This builds a nested data structure - a hash of hashes (or hash references). The outer hash contains a key for each unique $srcip (source IP address?) value. The value associated with this key is (a reference to) another hash which has a key for each unique $dstip (destination IP address?). I would guess this is trying to build a table of source/destination pairs. The value is always set to 1 so it's probably only being used for definedness.

foreach $srcip (keys(%srciphash))

This iterates the outer hash and executes the block for each key it finds.

foreach $dstip (keys(%{$srciphash{$srcip}}))

This iterates the inner hash for the currently selected outer hash. The block associated with this should be invoked once for each unique $srcip/$dstip pair.

---
print map { my ($m)=1<<hex($_)&11?' ':'';
$m.=substr('AHJPacehklnorstu',hex($_),1) }
split //,'2fde0abe76c36c914586c';
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