c:\@Work\Perl>perl -wMstrict -le
"print 'A: found 0x13!' if  unpack('H*',        'a1') =~ /13/;
 print 'B: found 0x13!' if  unpack('h*', qq{\x{1f}s}) =~ /13/;
"
A: found 0x13!
B: found 0x13!