If the input string is made of digits, you will see an hex like that you're describing. Consider that in ASCII the digits characters range from decimal 48, which is 0x30, to decimal 57, which is 0x39.

If you have numbers that you want to treat like integers, and they're in the range 0-255, you can put a chr in the chain:

#!/usr/bin/perl
use strict;
use warnings;
my @values = (0, 1, 5, 25, 100, 200, 255);
print join(", ", map { unpack "H*", chr } @values), $/;

__END__
00, 01, 05, 19, 64, c8, ff
[download]

You may also consider printf/sprintf with the X indicator:

#!/usr/bin/perl
use strict;
use warnings;
my @values = (0, 1, 5, 25, 100, 200, 255, 500, 1000);
print join(", ", map { sprintf "%X", $_ } @values), $/;

__END__
0, 1, 5, 19, 64, C8, FF, 1F4, 3E8
[download]

Note that this second solution works well with numbers beyond 255. You can also pad with zeroes on the left, just look in the docs for sprintf.