c:\@Work\Perl>perl -wMstrict -le
"use Data::Dump qw(pp);
 ;;
 for my $s ('a1', qq{\x{1f}s}) {
   print q{'H*' found 0x13! in }, pp($s) if unpack('H*', $s) =~ /13/;
   print q{'h*' found 0x13! in }, pp($s) if unpack('h*', $s) =~ /13/;
   }
"
'H*' found 0x13! in "a1"
'h*' found 0x13! in "a1"
'h*' found 0x13! in "\37s"