Alternatively, you could find just the keys shared by both hashes using grep

use v5.22;
use warnings;

my %hash1 = ( a => 1, b => 2, c => 3, );
my %hash2 = ( b => 4, e => 5, f => 6, c => 7, );


my @results = grep { exists $hash2{$_} } keys %hash1;

say join ',',@results;
#b,c
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