Re: Why is my code producing weird output?

[NetWallah]

The code works fine for me : Output:

$ perl pm1.pl < pm1-dat.txt
george:2~~14
nick:5~~10~~20
peter:3

My perl : This is perl 5, version 34, subversion 0 (v5.34.0) built for x86_64-linux-gnu-thread-multi

Your code uses an un-declared $a which is also used by sort.
Your perl seems to encounter side-effects of that.
I recommend you use a declared variable NOT named $a, or $b.

[hv]

Note that in the line for $a( sort keys %res ), the work for the sort is completed before the first value is assigned to $a. So while this might not be best practice, I do not think it is causing the problem in this case.