I don't think you need to build a new array, and I think any may be faster than grep because it doesn't always traverse the whole array and it potentially uses the C implementation (List::MoreUtils). I used $x instead of $a, which has special super powers. 
use warnings;
use strict;
use List::MoreUtils qw(any);

my %hoa = (
    x => [ qw(a b c d) ],
    y => [ qw(e f g) ],
    z => [ qw(h i c j) ],
);

my $x = 'c';

for my $k (keys %hoa) {
    print "key $k has $x\n" if any { $_ eq $x } @{ $hoa{$k} };
}

__END__

key x has c
key z has c

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In reply to Re: Have hash of arrays. Want to test if variable is a member of any of the arrays by toolic
in thread Have hash of arrays. Want to test if variable is a member of any of the arrays by batrams

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