Have you tried use warnings or used -w? They enable warnings to detect dubious practices.
Have you tried use strict? It prevents you from using symbolic references, makes you predeclare any subroutines that you call as bare words, and (probably most importantly) forces you to predeclare your variables with my, our, or use vars.
Did you check the return values of each and every system call? The operating system (and thus Perl) tells you whether they worked, and if not why.
open(FH, "> /etc/cantwrite")
or die "Couldn't write to /etc/cantwrite: $!\n";Did you read perltrap? It's full of gotchas for old and new Perl
programmers and even has sections for those of you who are upgrading
from languages like awk and C.
Have you tried the Perl debugger, described in perldebug? You can step through your program and see what it's doing and thus work out why what it's doing isn't what it should be doing.