By using qr{} I am telling Perl the string inside will be used in a regex. See http://perldoc.perl.org/perlop.html#Regexp-Quote-Like-Operators. The most common reason to do this is to save time when you are using the same regex over and over; I use it because it often seems to make sure Perl interprets the regex in the way I expect.

map {block} @array returns an array created by executing {block} once for each element of @array, each time assigning one value to $_.

@a=(1,2,3);
@a_plus_1 = map { $_ + 1 } @a;

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The block, which in this example is $_ + 1, will be execute 3 times, once for each value in @a. It will put the results also in an array, so the values in @a_plus_1 will be (2,3,4).

In my solution, I have the map return two values separated by a comma. This is one way to define a hash. You can see this using the debugger:

perl -d -e 1
Loading DB routines from perl5db.pl version 1.28
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(-e:1):   1
  DB<1> %h=(1,2,3,4)

  DB<2> print $h{1}
2

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Dum Spiro Spero

In reply to Re^3: Parsing file in Perl post processing by GotToBTru
in thread Parsing file in Perl post processing by gbwien

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