It’s not exactly a “simple” question, so don’t beat yourself up. The issue is that with a single /e, the RHS is understood to be code whose eval’d result is used for the replacement. What is that RHS? It’s $1. If you evaluated $1, you find that contains the string $var. It does not contain … Read more
I think you are using a pretty good one. XML::LibXML, Matt Sergeant and Christian Glahn’s Perl interface to Daniel Velliard’s libxml2 is one of the faster XML Parsers that I know of.
bbe is a “sed for binary files”, and should work more efficiently for large binary files than hexdumping/reconstructing. An example of its use: $ bbe -e ‘s/original/replaced/’ infile > outfile Further information on the man page.
print “Number of lines: $nids\n”; print “Content: $ids\n”; How did Perl complain? print $ids should work, though you probably want a newline at the end, either explicitly with print as above or implicitly by using say or -l/$\. If you want to interpolate a variable in a string and have something immediately after it that … Read more
You want to use the substr() function. $shortened = substr( $long, 0, 50 ); # 50 characters long, starting at the beginning. For more, use perldoc perldoc -f substr In your case, it would be: $str=”abcd”; $short = substr( $str, 0, 3 );
Use $. (see perldoc perlvar).
Due to the low precedence of the ‘or’ operator, or3 parses as follows: sub or3 { my ($a,$b) = @_; (return $a) or $b; } The usual advice is to only use the ‘or’ operator for control flow: @info = stat($file) or die; For more discussion, see the perl manual: http://perldoc.perl.org/perlop.html#Logical-or-and-Exclusive-Or
Two advantages come to mind: Simplicity: direct access to all wonderful linux tools wc, ls, cat, grep, sed… etc. Why constantly use python’s subprocess module? I’m increasingly fond of using gnu parallel, with which you can execute your bash scripts in parallel. E.g. from the man page, batch create thumbs of all jpgs in directory … Read more
You can do it in a single assignment: my %hash; @hash{@array1} = @array2; It’s a common idiom. From perldoc perldata on slices: If you’re confused about why you use an ‘@’ there on a hash slice instead of a ‘%’, think of it like this. The type of bracket (square or curly) governs whether it’s … Read more
use constant actually makes constant subroutines. To do what you want, you need to explicitly call the sub: use constant X => 1; my %x = ( &X => ‘X’); or use constant X => 1; my %x = ( X() => ‘X’);