#use strict; use warnings; 
my $a=''; # entered by holding down cntrl pressing _ (shift+-) 
print "ord:".ord($a)."\n";
print 'hex:'.unpack("H*", $a)."\n";
my $b="\x1f"; 
if ($a eq $b) {print '$a eq $b'."\n";} 
my $bb=\x1f; 
print $bb."\n";