#!/usr/bin/perl -w use Data::Dumper; print "Case 1: non existent\n"; exists $x->{'y'}->{'z'}; print Dumper $x; print "Case 2: undef\n"; $x = undef; exists $x->{'y'}->{'z'}; print Dumper $x; print "Case 3: hashref\n"; $x = {}; exists $x->{'y'}->{'z'}; print Dumper $x; print "Case 4: stopper scalar\n"; $x = 'stopper'; exists $x->{'y'}->{'z'}; print Dumper $x; print "Case 5: Even assignment won't do, and won't trigger warning or runtime error!\n"; $x = 'stop2'; $x->{'y'}->{'z'} = 'something'; print Dumper $x; print "Case 6: use strict is your friend :)\n"; eval { use strict 'refs'; $x = 'stop3'; $x->{'y'}->{'z'} = 'something else'; print Dumper $x; }; $@ and print $@;