I would put the print into two sections.

print "Hash: hash1"
check_limit(\%hash1);
 
sub check_limit {
        my $hname = $_[0];
 
        my $num = 0; for (keys %{$hname}) { $num++ };
        print " has $num keys\n";
}
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Or then use another variable to give the name to subroutine.