[perl/en] Use more single quotes and explain single vs double quotes (#2710)

* [perl/en] Explain single vs double quotes

Explains an example of variable interpolation and escape codes in a double quoted string.

* add section about interpolating arrays and email in double quotes trap

1 files changed, 16 insertions, 0 deletions

diff --git a/perl.html.markdown b/perl.html.markdown
index 93eabea9..17a538e3 100644
--- a/perl.html.markdown
+++ b/perl.html.markdown
@@ -37,10 +37,14 @@ use warnings;
 #  A scalar represents a single value:
 my $animal = "camel";
 my $answer = 42;
+my $display = "You have $answer ${animal}s.\n";
 
 # Scalar values can be strings, integers or floating point numbers, and
 # Perl will automatically convert between them as required.
 
+# Strings in single quotes are literal strings. Strings in double quotes
+# will interpolate variables and escape codes like "\n" for newline.
+
 ## Arrays
 #  An array represents a list of values:
 my @animals = ("camel", "llama", "owl");
@@ -58,6 +62,18 @@ my $second = $animals[1];
 my $num_animals = @animals;
 print "Number of numbers: ", scalar(@numbers), "\n";
 
+# Arrays can also be interpolated into double-quoted strings, and the
+# elements are separated by a space character by default.
+
+print "We have these numbers: @numbers\n";
+
+# Be careful when using double quotes for strings containing symbols
+# such as email addresses, as it will be interpreted as a variable.
+
+my @example = ('secret', 'array');
+my $oops_email = "foo@example.com"; # 'foosecret array.com'
+my $ok_email = 'foo@example.com';
+
 ## Hashes
 #   A hash represents a set of key/value pairs: