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-rw-r--r--perl.html.markdown57
1 files changed, 49 insertions, 8 deletions
diff --git a/perl.html.markdown b/perl.html.markdown
index 3cbd2801..8811dd08 100644
--- a/perl.html.markdown
+++ b/perl.html.markdown
@@ -8,9 +8,9 @@ contributors:
- ["Dan Book", "http://github.com/Grinnz"]
---
-Perl 5 is a highly capable, feature-rich programming language with over 25 years of development.
+Perl is a highly capable, feature-rich programming language with over 25 years of development.
-Perl 5 runs on over 100 platforms from portables to mainframes and is suitable for both rapid prototyping and large scale development projects.
+Perl runs on over 100 platforms from portables to mainframes and is suitable for both rapid prototyping and large scale development projects.
```perl
# Single line comments start with a number sign.
@@ -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");
@@ -51,6 +55,25 @@ my @mixed = ("camel", 42, 1.23);
# indicate one value will be returned.
my $second = $animals[1];
+# The size of an array is retrieved by accessing the array in a scalar
+# context, such as assigning it to a scalar variable or using the
+# "scalar" operator.
+
+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:
@@ -67,6 +90,11 @@ my %fruit_color = (
# Hash elements are accessed using curly braces, again with the $ sigil.
my $color = $fruit_color{apple};
+# All of the keys or values that exist in a hash can be accessed using
+# the "keys" and "values" functions.
+my @fruits = keys %fruit_color;
+my @colors = values %fruit_color;
+
# Scalars, arrays and hashes are documented more fully in perldata.
# (perldoc perldata).
@@ -124,26 +152,30 @@ while (condition) {
...
}
-
+my $max = 5;
# for loops and iteration
-for (my $i = 0; $i < $max; $i++) {
+for my $i (0 .. $max) {
print "index is $i";
}
-for (my $i = 0; $i < @elements; $i++) {
- print "Current element is " . $elements[$i];
-}
-
for my $element (@elements) {
print $element;
}
+map {print} @elements;
+
# implicitly
for (@elements) {
print;
}
+# iterating through a hash (for and foreach are equivalent)
+
+foreach my $key (keys %hash) {
+ print $key, ': ', $hash{$key}, "\n";
+}
+
# the Perlish post-condition way again
print for @elements;
@@ -170,8 +202,11 @@ $x =~ s/foo/bar/g; # replaces ALL INSTANCES of foo with bar in $x
# You can open a file for input or output using the "open()" function.
+# For reading:
open(my $in, "<", "input.txt") or die "Can't open input.txt: $!";
+# For writing (clears file if it exists):
open(my $out, ">", "output.txt") or die "Can't open output.txt: $!";
+# For writing (appends to end of file):
open(my $log, ">>", "my.log") or die "Can't open my.log: $!";
# You can read from an open filehandle using the "<>" operator. In
@@ -182,6 +217,12 @@ open(my $log, ">>", "my.log") or die "Can't open my.log: $!";
my $line = <$in>;
my @lines = <$in>;
+# You can write to an open filehandle using the standard "print"
+# function.
+
+print $out @lines;
+print $log $msg, "\n";
+
#### Writing subroutines
# Writing subroutines is easy: