use strict;
use vars qw($hashRef1 $hashRef2);
#code that puts values into the hashes

my @keyIntersection =
  grep exists($hashRef2->{$_}), keys %$hashRef1;

# Or if you just want to know if there are any

use List::Util;
my $hasInt =
   first {exists $hashRef2->{$_}} keys %$hashRef1;
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$hasInt will be undef unless there's an intersection.
But be careful, it will be 0 if the first interecting key is '0'

throop