shebang line:
#!/usr/bin/env perl

- this is dependable as all *nix systems should have /usr/bin/env and perl witll return the path for the env variable

problem is perl flags:

#!/usrl/local/perl -w does not work with the above
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glob foo.*  is same as ls foo.*
 
foreach my $file (glob "foo.*"){}
 
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use FindBin qw($Bin);
locates the path of the original script

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keep contants close to where they are being used:

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open (FH,...)
FH is global.. that is BAD
 
much better to use open(my $fh,...)

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'redo' keyword in perl redoes the iteration

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qr// -- quotes the regex

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last 2 goes up two outer loops?

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while(.... my ($st,$pat) = each (%patterns)){
 
more effiicient than
 
foreach( my $key (keys %patterns)){}

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Data::Dumper
Data::Serializer -- does everything... gozer says

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use Benchmark
Benchmark::cmpthese()
Benchmark::timethese()

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my @foo = map{chomp; $_; } @bar  #iterated through each @bar, and does something, and pushes on @foo

more efficient than doing it yourself with your own loop

example:
my @multiples_of_2 = map{$_ * 2} @ints;