Hi. Thats not likely; This is your program with the missing data filled in

#!/usr/bin/perl --
use strict;
use warnings;
my @nets = qw/ a b c d /;
# my $ioRef = $moduleRef->{modRef}{$moduleName}{ioRef};
my $ioRef = { qw/ q q c c d /, undef }; ## Data::Dump::dd( $ioRef )
for my $net ( @nets ){
    print "checking $net\n";
    if( defined $ioRef->{$net} ){
        print "defined $net $ioRef->{$net} \n";
    }
}
__END__
checking a
checking b
checking c
defined c c
checking d
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You're saying a/b are defined inside $ioRef ... but thats highly unlikely (impossible)

What does that mean? You need to post runnable code