You are probably using the wrong data structure and should use a hash of arrays, e.g.

my %visited_by = (
    Peter => [ qw(Sydney Melbourne Perth) ],
    Paul  => [ qw(Shrewsbery Cambridge) ],
    Mary  => [ qw(Paris London Rome) ],
);

print "Mary has been to @{ $visited_by{Mary} }\n";

Output
Mary has been to Paris London Rome
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