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Task/Quoting-constructs/Perl/quoting-constructs.pl

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+# 20221202 Perl programming solution
+
+use strict;
+use warnings;
+
+print <<`EXEC`                     # superfluous alternative to qx/ / and ` `
+sleep 2; ls /etc/resolv.conf
+EXEC
+;
+            # only with quoted begin tag then you can have spaces in between
+print <<END # so <<  'END' or <<     "END" and semi-colon is always optional
+Make sure that the end tag must be exactly the same as the begin tag.
+END
+; # the above wouldn't have worked had it been something like
+  # END␣ ␣ ␣ (with redundant trailing spaces)
+
+print <<"HERE1", <<"HERE2"    # it is also possible to stack heredocs
+Hello from HERE1
+HERE1
+Hello from HERE2
+HERE2
+;
+
+my $haystack = 'Santa says HoHoHo'; # a quoted pattern expanded before
+my $needle   = "\x48\x6F";          # the regex is interpreted
+print "1) Found.\n" if $haystack =~  /$needle{3}/;   # Matches Hooo
+print "2) Found.\n" if $haystack =~ /($needle){3}/;  # Do what you mean
+
+                  # due to autoconversion, things may still work the same
+{  use Benchmark; # under (usually overlooked) scalar interpolation
+   my ( $iterations, $x, $y ) = 1e7, rand, rand;
+   timethese( $iterations, { 'normal'   => ' $x  +  $y',
+                             'useless'  => '"$x" + "$y"' } );
+} # however in the 2nd case the boxing and unboxing are unnecessary
+
+{ # the following illustrate some behaviors under array interpolation
+   my @Y_M_D = sub{$_[5]+1900,$_[4]+1,$_[3]}->(localtime(time));
+   local  $\ = "\n";
+   print  @Y_M_D;     # YMD
+   print "@Y_M_D";    # Y M D
+   local  $, = '-';   # output field separator
+   print  @Y_M_D;     # Y-M-D
+   print "@Y_M_D";    # Y M D
+   local  $" = '_';   # interpolated list separator
+   print "@Y_M_D";    # Y_M_D
+}