Nice solution! I didn't know about '/' in pack.

It's not quite perfect, though. It treats the empty string and undef as equal (there may be more ways to break it - this is just the first one I thought of): 

my $signature_1 = pack( '(J/a*)*', '', undef );
my $signature_2 = pack( '(J/a*)*', undef, '' );

printf( "Signatures are %s\n",
        ( $signature_1 eq $signature_2 ) ? 'equal' : 'unequal' ); # eq
+ual!

[download]

These cases were not specified in the OP. I apologize for being pedantic. :-)

In reply to Re^3: Fast way to check if a sort was done (using stringification is *broken*) by bobf
in thread Fast way to check if a sort was doen by Outaspace

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