Use map to transform one list of values into a new list; use for to iterate over a list performing some operations. In both of your cases you're not really generating a new list. The first one could be done as  my %byFile = map { chomp; split( /\s+/, $_, 2 ) } <DATA>, but I'd personally use the for instead. Considering your second loop is a single statement I'd probably write it as print "$_\t=>$byFile{$_}\n" for keys %byFile, but definately not using map.

In reply to Re: I don't get map. How would I use map here? by Fletch
in thread I don't get map. How would I use map here? by Plankton

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